Induction-Based Micro-Volume Heating System

ABSTRACT

Ablation catheters and systems include multiple inline chambers for containing and heating an ablative agent. The heating chamber includes one or more channels to increase the contact surface area of the ablative agent with the walls of the heating chamber to provide more efficient heating. Induction heating is used to heat a chamber and vaporize a fluid within by wrapping a coil about a ferromagnetic chamber and providing an alternating current to the coil. A magnetic field is created in the area surrounding the chamber which induces electric current flow in the chamber, heating the chamber and vaporizing the fluid inside. Positioning elements help maintain the device in the proper position with respect to the target tissue and also prevent the passage of ablative agent to normal tissues.

CROSS-REFERENCE

The present application is a continuation-in-part application of U.S.patent application Ser. No. 14/594,444, entitled “Method and Apparatusfor Tissue Ablation” and filed on Jan. 12, 2015, which is acontinuation-in-part application of U.S. patent application Ser. No.14/158,687 (“'687 application”), of the same title and filed on Jan. 17,2014, which relies on U.S. Provisional Patent Application No.61/753,831, of the same title and filed on Jan. 17, 2013, for priority.

The '687 application is also a continuation-in-part application of U.S.patent application Ser. No. 13/486,980 (“'980 application”), entitled“Method and Apparatus for Tissue Ablation” and filed on Jun. 1, 2012,which relies on U.S. Provisional Patent Application No. 61/493,344, ofthe same title and filed on Jun. 3, 2011, for priority.

The '980 application is also a continuation-in-part application of U.S.patent application Ser. No. 12/573,939, entitled “Method and Apparatusfor Tissue Ablation” and filed on Oct. 6, 2009, which relies on U.S.Provisional Patent Application No. 61/102,885, of the same title andfiled on Oct. 6, 2008, for priority.

The aforementioned applications are herein incorporated by reference intheir entirety.

FIELD

The present specification relates to devices and systems configured togenerate heat. More particularly, the present specification relates toimproved devices and systems which use electromagnetic induction createdby a coil positioned around an electrically conducting material, andmore particularly a ferromagnetic material, to generate heat.

BACKGROUND

Ablation, as it pertains to the present specification, relates to theremoval or destruction of a body tissue, usually by surgery orintroduction of a noxious substance. Ablation is commonly used toeliminate diseased or unwanted tissues, such as, but not limited to,cysts, polyps, tumors, hemorrhoids, and other similar lesions.

Colon polyps affect almost 25% of the population over the age of 50.While most polyps are detected on colonoscopy and easily removed using asnare, flat sessile polyps are hard to remove using the snare techniqueand carry a high risk of complications, such as bleeding andperforation. Recently, with improvement in imaging techniques, more flatpolyps are being detected. Endoscopically unresectable polyps requiresurgical removal. Most colon cancer arises from colon polyps and, safeand complete resection of these polyps is imperative for the preventionof colon cancer.

Barrett's esophagus is a precancerous condition effecting 10-14% of theUS population with gastro esophageal reflux disease (GERD) and is theproven precursor lesion of esophageal adenocarcinoma, the fastest risingcancer in developed nations. The incidence of the cancer has risen over6 fold in the last 2 decades and the mortality rate has risen by 7 fold.The 5-year mortality rate from esophageal cancer is 85%. Ablation ofBarrett's epithelium has shown to prevent its progression to esophagealcancer.

Benign Prostatic Hyperplasia (BPH) is a non-cancerous condition of theprostate defined by an increase in the number of prostatic stromal andepithelial cells, resulting in an overall increase in the size of theprostate. The increase in size can constrict the prostatic urethra,resulting in urinary problems such as an increase in urinary frequency,urinary hesitancy, urinary retention, dysuria, and an increase in theoccurrence of urinary tract infections (UTI's). Approximately 50% of menshow histological evidence of BPH by age 50, which rises to 75% by age80. About half of these men have symptoms. Although BPH does not lead tocancer, it can have a significant impact on urinary health and qualityof life. Therapies aimed at alleviating the symptoms associated with BPHinclude those involved with reducing prostate size, such astransurethral microwave thermotherapy and transurethral needle ablation,which uses RF energy. When such less invasive therapies are ineffective,surgery, such as transurethral resection of the prostate, often becomesnecessary.

Prostate cancer is diagnosed in approximately 8% of men between the agesof 50 and 70 and tends to occur in men as they grow older. Menexperiencing symptoms with prostate cancer often exhibit symptomssimilar to those encountered with BPH and can also suffer from sexualproblems caused by the disease. Typically, men diagnosed with prostatecancer when the cancer is at an early stage have a very good prognosis.Therapy ranges from active surveillance to surgery and radiation andchemotherapy depending on the severity of the disease and the age of thepatient.

Dysfunctional uterine bleeding (DUB), or menorrhagia, affects 30% ofwomen in reproductive age. The associated symptoms have considerableimpact on a woman's health and quality of life. The condition istypically treated with endometrial ablation or a hysterectomy. The ratesof surgical intervention in these women are high. Almost 30% of women inthe US will undergo hysterectomy by the age of 60, with menorrhagia orDUB being the cause for surgery in 50-70% of these women. Endometrialablation techniques have been FDA approved for women with abnormaluterine bleeding and with intramural fibroids less than 2 cm in size.The presence of submucosal uterine fibroids and a large uterus size havebeen shown to decrease the efficacy of standard endometrial ablation. Ofthe five FDA approved global ablation devices, only microwave ablationhas been approved for use where the submucosal fibroids are less than 3cm in size and are not occluding the endometrial cavity and,additionally, for large uteri up to 14 cm in width.

The known ablation treatments for Barrett's esophagus include lasertreatment, ultrasonic ablation, photodynamic therapy (PDT) usingphoto-sensitizer drugs, multipolar electrocoagulation, such as by use ofa bicap probe, argon plasma coagulation (APC), radiofrequency ablation,and cryoablation. The treatments are delivered with the aid of anendoscope wherein devices are passed through the channel of theendoscope or alongside the endoscope.

Conventional techniques have inherent limitations, however, and have notfound widespread clinical applications. First, most of the hand heldablation devices (bicap probe, APC, cryoablation) are point and shootdevices that create small foci of ablation. This ablation mechanism isoperator dependent, cumbersome, and time consuming. Second, because thetarget tissue is moving due to patient movement, respiration movement,normal peristalsis, and vascular pulsations, the depth of ablation ofthe target tissue is inconsistent and results in a non-uniform ablation.Superficial ablation results in incomplete ablation with residualneoplastic tissue left behind. Deeper ablation results in complicationssuch as bleeding, stricture formation, and perforation. All of theselimitations and complications have been reported with conventionaldevices.

For example, radiofrequency ablation uses a rigid bipolar balloon basedelectrode and radiofrequency thermal energy. The thermal energy isdelivered by direct contact of the electrode with the diseased Barrett'sepithelium allowing for a relatively uniform, large area ablation.However, the rigid electrode does not accommodate for variations inesophageal size and is ineffective in ablating esophageal tissue in atortuous esophagus, proximal esophageal lesions as an esophagus narrowstoward the top, and esophageal tissue at the gastroesophageal junctiondue to changes in the esophageal diameter. Nodular disease in Barrett'sesophagus also cannot be treated using the rigid bipolar RF electrode.Due to its size and rigidity, the electrode cannot be passed through thescope. In addition, sticking of sloughed tissue to the electrode impedesdelivery of radiofrequency energy, resulting in incomplete ablation. Theelectrode size is limited to 3 cm, thus requiring repeat applications totreat larger lengths of Barrett's esophagus.

Photodynamic therapy (PDT) is a two part procedure that involvesinjecting a photo-sensitizer that is absorbed and retained by theneoplastic and pre-neoplastic tissue. The tissue is then exposed to aselected wavelength of light which activates the photo-sensitizer andresults in tissue destruction. PDT is associated with complications suchas stricture formation and photo-sensitivity which has limited its useto the most advanced stages of the disease. In addition, patchy uptakeof the photosensitizer results in incomplete ablation and residualneoplastic tissue.

Cryoablation of the esophageal tissues via direct contact with liquidnitrogen has been studied in both animal models and humans and has beenused to treat Barrett's esophagus and early esophageal cancer. A spraycatheter that directly sprays liquid N₂ or CO₂ (cryoablation) or argon(APC) to ablate Barrett's tissue in the esophagus has been described.These techniques suffer the shortcoming of the traditional hand-helddevices. Treatment using this probe is cumbersome and requires operatorcontrol under direct endoscopic visualization. Continuous movement inthe esophagus due to respiration or cardiac or aortic pulsations ormovement causes an uneven distribution of the ablative agent and resultsin non-uniform and/or incomplete ablation. Close or direct contact ofthe catheter to the surface epithelium may cause deeper tissue injury,resulting in perforation, bleeding, or stricture formation. Too distanta placement of the catheter due to esophageal movement will result inincomplete Barrett's epithelium ablation, requiring multiple treatmentsessions or buried lesions with a continued risk of esophageal cancer.Expansion of cryogenic gas in the esophagus results in uncontrolledretching which may result in esophageal tear or perforation requiringcontinued suctioning of cryogen.

Colon polyps are usually resected using snare resection with or withoutthe use of monopolar cautery. Flat polyps or residual polyps after snareresection have been treated with argon plasma coagulation or lasertreatment. Both these treatments have the previously mentionedlimitations. Hence, most large flat polyps undergo surgical resectiondue to the high risk of bleeding, perforation, and residual diseaseusing traditional endoscopic resection or ablation techniques.

Most of the conventional balloon catheters traditionally used for tissueablation either heat or cool the balloon itself or a heating elementsuch as radio frequency (RF) coils mounted on the balloon. This requiresdirect contact of the balloon catheter with the ablated surface. Whenthe balloon catheter is deflated, the epithelium sticks to the catheterand sloughs off, thereby causing bleeding. Blood can interfere with thedelivery of energy, i.e. energy sink. In addition, reapplication ofenergy will result in deeper burn in the area where superficial lininghas sloughed. Further, balloon catheters cannot be employed fortreatment in non-cylindrical organs, such as the uterus or sinuses, andalso do not provide non-circumferential or focal ablation in a holloworgan. Additionally, if used with cryogens as ablative agents, whichexpand exponentially upon being heated, balloon catheters may result ina closed cavity and trap the escape of cryogen, resulting incomplications such as perforations and tears.

Metal stents have been used for palliation of malignant obstruction.However, tumor ingrowth continues to be a significant problem affectingstent longevity. Covered stents provide a good solution for in-growth,however, tumor compression can lead to stent blockage and dysfunction.Traditional coverings on the stents, such as silicone, have poor thermalconductivity and do not allow for successful thermal therapy after thestent has been deployed.

Accordingly, there is a need in the art for improved devices and methodsfor delivering ablative agents to a tissue surface, for providing aconsistent, controlled, and uniform ablation of the target tissue, andfor minimizing the adverse side effects of introducing ablative agentsinto a patient. What is also needed is a stent that provides the abilityto deliver ablative therapy to an inoperable tumor post deployment.

SUMMARY

The present specification discloses an induction-based heating systemcomprising: a heating chamber comprising a ferromagnetic core housedwithin a non-ferromagnetic housing; a resonant circuit comprising acapacitor and an induction coil positioned around said non-ferromagnetichousing; a rectifier adapted to receive alternating current line voltageand provide direct current power; a phase control circuit configured toplace said alternating current line voltage in electrical communicationwith said rectifier at each half wave of the alternating current linevoltage; and an H bridge inverter circuit configured to apply rectifiedline voltage across said resonant circuit, wherein said H bridgeinverter is adapted to apply rectified line voltage to said resonantcircuit and adapted to switch off when a magnetic field generated by theinduction coil is fully saturated.

Optionally, the heating chamber comprises a layer of non-thermoplasticinsulation concentrically positioned around the ferromagnetic core andseparated from the ferromagnetic core by a space. Optionally, thenon-ferromagnetic housing comprises a thermoplastic material wherein thenon-ferromagnetic housing is concentrically positioned around the layerof non-thermoplastic insulation. Optionally, the induction-based heatingsystem further comprises a second layer of non-thermoplastic insulationconcentrically positioned around the non-ferromagnetic housing andbetween said non-ferromagnetic housing and the induction coil.Optionally, at least one of said layer of non-thermoplastic insulationand said second layer of non-thermoplastic insulation comprises mica.

The thermoplastic material may comprise at least one of ABS, acetal,polyamide, PEEK, and polyvinylidene difluoride (PVDF).

Optionally, the ferromagnetic core is a unitary member comprising aplurality of grooves encircling an outer periphery of the unitarymember. Optionally, the ferromagnetic core is a cylindrical unitarymember having a first face transverse to a length of the cylindricalunitary member and a second face opposing the first face and transverseto the length of the cylindrical unitary member, wherein at least one ofthe first face and second face comprises a groove adapted to direct afluid from a surface of the first face to said plurality of grooves orfrom said plurality of grooves to a surface of the second face.

Optionally, the induction-based heating system further comprises aninduction coil support structure, wherein said induction coil supportstructure is configured to support the induction coil and slidablyreceive said heating chamber. Optionally, the induction coil has a totallength wherein said heating chamber is adapted to move within theinduction coil support structure such that said ferromagnetic core isconfigured to move relative to the induction coil by at least fivepercent of the total length of the induction coil. Optionally, theinduction-based heating system further comprises a handle attached tosaid heating chamber, wherein said handle has a total length and whereinsaid heating chamber is adapted to move within the induction coilsupport structure such that said ferromagnetic core is configured tomove relative to the induction coil support structure by at least fivepercent of the total length of the handle. Optionally, theinduction-based heating system further comprises a handle and acatheter, wherein said heating chamber is attached to the catheter andsaid handle, wherein said handle, heating chamber, and catheter areconfigured such that moving said handle causes said heating chamber tomove relative to the induction coil and causes said catheter to move.Optionally, the induction coil has a total length wherein said heatingchamber is adapted to move within the induction coil support structuresuch that said ferromagnetic core is configured to move relative to theinduction coil by at least five percent of the total length of theinduction coil.

Optionally, the H bridge inverter circuit is configured to switch on andoff at a frequency between 10 kHz and 100 kHz.

Optionally, a conversion of energy in said magnetic field to energy insaid heat has an efficiency of 60% or greater.

Optionally, the magnetic field has a vibration of 15 to 25 kHz.

Optionally, the induction-based heating system further comprises controlcircuitry, wherein the control circuitry is configured to turn off atransmission of electrical energy to the H bridge inverter circuit oncethe magnetic field is fully saturated.

Optionally, when the H bridge inverter is turned off and the magneticfield collapses, a kickback pulse is generated and wherein at least onecapacitor is configured to absorb energy from said kickback pulse.Optionally, at least one capacitor is configured to discharge electricalenergy into said induction coil.

Optionally, the phase control circuit is configured to turn on the linevoltage to the rectifier and H bridge inverter circuit when saidcapacitor has discharged at least 90% of said electrical energy intosaid induction coil.

Optionally, the phase control circuit comprises a triac phase controlcircuit.

Optionally, the phase control circuit is configured to turn off atzero-point crossings of said line voltage. The induction-based heatingsystem may further comprise a drive circuit, wherein said drive circuitis configured to trigger the phase control circuit.

Optionally, the H-bridge inverter comprises four switches and whereinevery 10 μsec to 50 μsec two of said four switches are switched closedand two of said four switches are switched open. Optionally, every 10μsec to 50 μsec the magnetic field is driven to zero and a polarity ofthe magnetic field is reversed.

Optionally, at each half-wave of the line voltage, the H bridge invertercircuit actively drives up the resonant circuit to replenish lostenergy.

Optionally, the non-ferromagnetic housing has a length ranging from 2.75inches to 3.75 inches, an inner diameter ranging from 7/32 inches to11/32 inches, and an outer diameter ranging from ⅜ inches to 0.5 inches.Optionally, the ferromagnetic core has a length ranging from 1.5 inchesto 2.5 inches and a diameter ranging from 3/16 inches to 5/16 inches.Optionally, the ferromagnetic core has a surface area to volume ratiothat is equal to, or greater than, 2(D₁+L)/D₂×L, where D₁ is a shortestcross-sectional dimension of the ferromagnetic core, D₂ is a longestcross-sectional dimension of the ferromagnetic core, and L is a lengthof the ferromagnetic core.

The present specification also discloses a method of performinginduction-based heating comprising: providing a closed loop fluidchannel, wherein the closed loop fluid channel comprises a heatingchamber having a non-ferromagnetic housing with an input port on a firstend and an output port on a second end and a ferromagnetic core housedwithin the non-ferromagnetic housing, a catheter attached to the outputport, a handle attached to the input port, a fluid channel positionedwithin said handle, a fluid source in fluid communication with the fluidchannel, and an induction coil support structure, wherein the inductioncoil support structure is configured to attach to an endoscope, whereinthe induction coil support structure supports an induction coil, andwherein the heating chamber is slidably positioned within the inductioncoil support structure, thereby positioning said induction coil aroundthe non-ferromagnetic housing; inserting the catheter into a channel ofan endoscope; repeatedly electrically driving a circuit in electricalcommunication with the induction coil to generate a magnetic field inthe induction coil and cause heat to be generated in said ferromagneticcore; physically moving the handle to cause said catheter to move withinsaid channel of the endoscope, wherein moving said handle causes theheating chamber to move relative to the induction coil; and initiating aflow of fluid through said closed loop fluid channel, wherein said flowof fluid passes through said ferromagnetic core and absorbs a portion ofsaid heat generated in said ferromagnetic core.

Optionally, the fluid is water and said water is transformed into steamas it passes through the heating chamber and into said catheter. Thesteam may have a water content in a range of 1% to 95% when it exitsfrom said catheter. The steam may have a temperature in a range of 99°C. to 101° C.

Optionally, the handle has a total length and wherein said heatingchamber is adapted to move within the induction coil support structuresuch that said ferromagnetic core is configured to move relative to theinduction coil support structure by at least five percent of the totallength of the handle.

Optionally, the induction coil has a total length wherein said heatingchamber is adapted to move within the induction coil support structuresuch that said ferromagnetic core is configured to move relative to theinduction coil by at least five percent of the total length of theinduction coil.

Optionally, the heating chamber comprises a layer of non-thermoplasticinsulation concentrically positioned around the ferromagnetic core andseparated from the ferromagnetic core by a space. Optionally, thenon-ferromagnetic housing comprises a thermoplastic material whereinsaid non-ferromagnetic housing is concentrically positioned around thelayer of non-thermoplastic insulation. Optionally, a second layer ofnon-thermoplastic insulation is concentrically positioned around thenon-ferromagnetic housing and between said non-ferromagnetic housing andthe induction coil. Optionally, at least one of said layer ofnon-thermoplastic insulation and said second layer of non-thermoplasticinsulation comprises mica. The thermoplastic material comprises at leastone of ABS, acetal, polyamide, PEEK, and PVDF.

The present specification also discloses an induction-based heatingsystem comprising: a heating chamber comprising an electricallyconducting core housed within an electrically non-conducting cylinder; atank circuit comprising a capacitor and an induction coil positionedaround said electrically non-conducting cylinder; a power sourceconfigured to provide a line voltage; a rectifier; a phase controlcircuit configured to place said line voltage in electricalcommunication with said rectifier; and at least one semiconductor switchconfigured to apply rectified line voltage across said tank circuit,wherein said phase control circuit is configured to repeatedly:electrically drive the at least one semiconductor switch to transferenergy to the tank circuit and generate a magnetic field in theinduction coil; and turn off a transmission of electrical energy to thetransistor to cause said magnetic field to collapse, electrical currentto flow between said capacitor and coil, and heat to be generated insaid heater core.

Optionally, said electrically conducting core comprises a ferromagneticmaterial. Optionally, said electrically non-conducting cylindercomprises a non-ferromagnetic material. Optionally, said tank circuit isa parallel tank circuit or a series tank circuit. A tank voltage may bealternating between 10 kHz and 100 kHz.

A conversion of energy in said magnetic field to energy in saidelectrically conducting core may have an efficiency of 60% or greater.

The magnetic field may have a vibration of 15 to 25 kHz.

Optionally, the induction-based heating system further comprises controlcircuitry, wherein the control circuitry is configured to turn off atransmission of electrical energy to the at least one semiconductorswitch once the magnetic field is fully saturated.

Optionally, the induction-based heating system further comprises asecond capacitor wherein the phase control circuit is programmed to turnoff the at least one semiconductor switch to cause said tank circuit toresonate, said magnetic field to collapse, and electrical current toflow into said capacitor and said second capacitor.

The capacitor may be configured to discharge electrical energy into saidinduction coil. The phase control circuit may be configured to drive theat least one semiconductor switch when said capacitor has discharged 90%of said electrical energy into said induction coil.

Optionally, said at least one semiconductor switch is an insulated-gatebipolar transistor (IGBT) or metal-oxide-semiconductor field-effecttransistor (MOSFET). The insulated-gate bipolar transistor (IGBT) ormetal-oxide-semiconductor field-effect transistor (MOSFET) may beconfigured to operate substantially continuously.

Optionally, said phase control circuit is a triac phase control circuit.

The phase control circuit may be configured to connect said line voltageto said rectifier at each half-wave of the line voltage.

The phase control circuit may be configured to connect said line voltageto said rectifier at only a portion of each half-wave of the linevoltage thereby controlling the amount of energy transferred to the atleast one semiconductor switch.

The phase control circuit may be configured to adjust the energytransferred to the at least one semiconductor switch according to afeedback loop.

The phase control circuit may be configured to turn off at zero-pointcrossings of said line voltage.

Optionally, the induction-based heating system further comprises a drivecircuit, wherein said drive circuit is configured to trigger the phasecontrol circuit.

The electrically non-conducting cylinder may have a length ranging from0.5 inches to 5 inches, an inner diameter ranging from 7/32 inches to 2inches, and an outer diameter ranging from ¼ inches to 2.5 inches.

The electrically conducting core may have a length ranging from 0.4inches to 5 inches and a diameter ranging from 5/32 inches to 2 inches.

The electrically conducting core may be separated from the electricallynon-conducting cylinder by a space.

The electrically conducting core may have a surface area to volume ratiothat is equal to, or greater than, 2(D₁+L)/D₂×L, where D₁ is a shortestcross-sectional dimension of the electrically conducting core, D₂ is alongest cross-sectional dimension of the electrically conducting core,and L is a length of the electrically conducting core. The electricallyconducting core may be separated from the electrically non-conductingcylinder by a space.

The present specification also discloses an induction-based heatingsystem comprising: a heating chamber comprising an electricallyconducting core housed within an electrically non-conducting cylinder,wherein the electrically conducting core is separated from theelectrically non-conducting cylinder by a space and wherein theelectrically conducting core has a surface area to volume ratio that isequal to, or greater than, 2(D₁+L)/D₂×L, where D₁ is a shortestcross-sectional dimension of the electrically conducting core, D₂ is alongest cross-sectional dimension of the electrically conducting core,and L is a length of the electrically conducting core; a circuitcomprising a capacitor and an induction coil positioned around saidelectrically non-conducting cylinder; a power source configured toprovide a line voltage; a rectifier; a phase control circuit configuredto place said line voltage in electrical communication with saidrectifier; and at least one semiconductor switch configured to applyrectified line voltage across said circuit, wherein said phase controlcircuit is configured to repeatedly: electrically drive the at least onesemiconductor switch to transfer energy to the circuit and generate amagnetic field in the induction coil; and turn off a transmission ofelectrical energy to the at least one semiconductor switch to causeelectrical current to flow into between said capacitor and coil and heatto be generated in said heater core.

The present specification is also directed toward a device to performablation of endometrial tissue, comprising a catheter having a shaftthrough which an ablative agent can travel, a first positioning elementattached to said catheter shaft at a first position, wherein said firstpositioning element is configured to center said catheter in a center ofa cervix, and an optional second positioning element attached to saidcatheter shaft at a second position, wherein the shaft comprises aplurality of ports through which said ablative agent can be released outof said shaft and wherein said ports are located between said firstposition and second position.

Optionally, the first positioning element is conical. The firstpositioning element comprises an insulated membrane which can beconfigured to prevent an escape of thermal energy through the cervix.The second positioning element is disc shaped. The second positioningelement has a dimension which can be used to determine a uterine cavitysize. The second positioning element has a dimension which can be usedto calculate an amount of thermal energy needed to ablate theendometrial tissue. The device also includes at least one temperaturesensor, which can be used to control delivery of the ablative agent,such as steam.

Optionally, the second positioning element is separated from endometrialtissue to be ablated by a distance of greater than 0.1 mm. The firstpositioning element is a covered wire mesh. The first positioningelement is comprises a circular body with a diameter between 0.1 mm and10 cm. The second positioning element is oval and wherein said oval hasa long axis between 0.1 mm and 10 cm and a short axis between 0.1 mm and5 cm.

In another embodiment, the present specification is directed toward adevice to perform ablation of endometrial tissue, comprising a catheterhaving a hollow shaft through which steam can be delivered, a firstpositioning element attached to said catheter shaft at a first position,wherein said first positioning element is conical and configured tocenter said catheter in a center of a cervix, an optional secondpositioning element attached to said catheter shaft at a secondposition, wherein the second positioning element is disc shaped, aplurality of ports integrally formed in said catheter shaft, whereinsteam can be released out of said ports and directed toward endometrialtissue and wherein said ports are located between said first positionand second position; and at least one temperature sensor.

Optionally, the second positioning element has a dimension, which can beused to determine a uterine cavity size. The second positioning elementhas a dimension, which can be used to calculate an amount of thermalenergy needed to ablate the endometrial tissue. The temperature sensorsare used to control delivery of said ablative agent. The firstpositioning element comprises wire mesh. The second positioning elementhas a disc shape that is oval and wherein said oval has a long axisbetween 0.1 mm and 10 cm and a short axis between 0.1 mm and 5 cm.

In another embodiment, the catheter has a first shaft with a first lumenand a first positioning element which is used to position the catheterin a patient's cervix. Distal to the first positioning element, thecatheter shaft bifurcates into a separate second shaft and a separatethird shaft. The second shaft includes a second lumen and a secondpositioning element and the third shaft includes a third lumen and athird positioning element. The second and third positioning elements areconfigured to position the second and third shafts respectively, in anintramural portion or an isthmus of a patient's fallopian tube,partially or completely blocking the opening of each fallopian tube.Each of the two bifurcated catheter shafts can be controlledindividually in a coaxial fashion. Each of the bifurcated shafts has oneor more openings for the ablative agent to pass from the lumen of therespective shaft to the surrounding tissue. Each of the positioningelements is used to occlude the respective openings. In one embodiment,the bifurcated catheter shaft length is used to measure the distancefrom the cervix to the opening of fallopian tube which in turn is usedto calculate the amount of ablative agent needed to ablate the desiredtissue.

The prior art describes the need to provide an expansion mechanism toopen a collapsed hollow organ to provide uniform ablation. This isroutinely performed using balloons, shaped meshes or other structures.It is desirable to provide a method for ablation not requiring anexpansion mechanism. The present specification is also directed toward amethod of providing vapor to a hollow organ where the vapor heats theair in the hollow organ, thus expanding the organ for uniform deliveryof ablative energy. The vapor is released at a predetermined temperatureand pressure to cause adequate expansion of the desired tissue withoutover expanding the hollow organ and causing a tear or perforation.

The prior art also describes the need for an occlusive mechanism toprevent the flow of ablative energy out of the target tissue region. Itis desirable to provide a method for ablation which does not require theuse of an occlusive agent to prevent the flow of energy beyond thetargeted tissue to prevent damage to healthy tissue. The presentspecification is also directed toward a method of providing vapor to ahollow organ wherein the vapor does not escape substantially beyond thetarget tissue to be ablated. The vapor is released at a predeterminedtemperature and pressure to cause localization of vapor in the desiredtissue and condensation of the vapor in the desired tissue withoutescape of the vapor substantially beyond the targeted tissue, thuspreventing significant damage to normal tissue.

The present specification is also directed toward a vapor ablationdevice for ablation of endometrial tissue comprising a catheter designedto be inserted through a cervical os and into an endometrial cavity,wherein the catheter is connected to a vapor generator for generation ofvapor and includes at least one port positioned in the endometrialcavity to deliver the vapor into the endometrial cavity. The vapor isdelivered through the port and heats and expands the air in theendometrial cavity to maintain the endometrial cavity pressure below 200mm Hg and ideally below 50 mm of Hg. In one embodiment, an optionalpressure sensor measures the pressure and maintains the intracavitarypressure at the desired therapeutic level, wherein the endometrialcavity is optimally expanded to allow for uniform distribution ofablative energy without the risk of significant leakage of the ablativeenergy beyond the endometrial cavity and damage to the adjacent normaltissue.

The present specification is also directed toward a device to performablation of tissue in a hollow organ, comprising a catheter having ashaft through which an ablative agent can travel; a first positioningelement attached to said catheter shaft at a first position, whereinsaid first positioning element is configured to position said catheterat a predefined distance from the tissue to be ablated; and wherein theshaft comprises one or more port through which said ablative agent canbe released out of said shaft.

Optionally, the device further comprises a second positioning elementattached to said catheter shaft at a position different from said firstpositioning element. The first positioning element is at least one of aconical shape, disc shape, or a free form shape conformed to the shapeof the hollow organ. The second positioning element has predefineddimensions and wherein said predefined dimensions are used to determinethe dimensions of the hollow organ to be ablated. The first positioningelement comprises an insulated membrane. The insulated membrane isconfigured to prevent an escape of thermal energy. The secondpositioning element is at least one of a conical shape, disc shape, or afree form shape conformed to the shape of the hollow organ. The secondpositioning element has predefined dimensions and wherein saidpredefined dimensions are used to determine the dimensions of the holloworgan to be ablated. The second positioning element has a predefineddimension and wherein said predefined dimension is used to calculate anamount of thermal energy needed to ablate the tissue. The device furthercomprises at least one temperature sensor. The temperature sensor isused to control delivery of said ablative agent. The ablative agent issteam. The first positioning element is a covered wire mesh. The firstpositioning element comprises a circular body with a diameter between0.01 mm and 10 cm. The first positioning element is oval and whereinsaid oval has a long axis between 0.01 mm and 10 cm and a short axisbetween 0.01 mm and 9 cm.

In another embodiment, the present specification is directed to a deviceto perform ablation of tissue in a hollow organ, comprising a catheterhaving a hollow shaft through which steam can be delivered; a firstpositioning element attached to said catheter shaft at a first position,wherein said first positioning element is configured to position saidcatheter at a predefined distance from the surface of the hollow organ;a second positioning element attached to said catheter shaft at a secondposition, wherein the second positioning element is shaped to positionsaid catheter at a predefined distance from the surface of the holloworgan; a plurality of ports integrally formed in said catheter shaft,wherein steam can be released out of said ports and directed towardtissue to be ablated and wherein said ports are located between saidfirst position and second position; and at least one temperature sensor.

Optionally, the first positioning element has a predefined dimension andwherein said dimension is used to determine the size of the holloworgan. The second positioning element has a predefined dimension andwherein said dimension is used to calculate an amount of thermal energyneeded to ablate the tissue. The temperature sensor is used to controldelivery of said ablative agent. The first positioning element compriseswire mesh. The second positioning element has a disc shape that is ovaland wherein said oval has a long axis between 0.01 mm and 10 cm and ashort axis between 0.01 mm and 9 cm.

In another embodiment, the present specification is directed to a deviceto perform ablation of the gastrointestinal tissue, comprising acatheter having a shaft through which an ablative agent can travel; afirst positioning element attached to said catheter shaft at a firstposition, wherein said first positioning element is configured toposition the catheter at a fixed distance from the gastrointestinaltissue to be ablated, and wherein said first positioning element isseparated from an ablation region by a distance of between 0 mm and 5cm, and an input port at a second position and in fluid communicationwith said catheter shaft in order to receive said ablative agent whereinthe shaft comprises one or more ports through which said ablative agentcan be released out of said shaft.

Optionally, the first positioning element is at least one of aninflatable balloon, wire mesh disc or cone. By introducing said ablativeagent into said ablation region, the device creates a gastrointestinalpressure equal to or less than 5 atm. The ablative agent has atemperature between −100 degrees Celsius and 200 degrees Celsius. Thecatheter further comprises a temperature sensor. The catheter furthercomprises a pressure sensor. The first positioning element is configuredto abut a gastroesophageal junction when placed in a gastric cardia. Theports are located between said first position and second position. Thediameter of the positioning element is between 0.01 mm and 100 mm. Theablative agent is steam. The first positioning element comprises acircular body with a diameter between 0.01 mm and 10 cm.

In another embodiment, the present specification is directed toward adevice to perform ablation of esophageal tissue, comprising a catheterhaving a hollow shaft through which steam can be transported; a firstpositioning element attached to said catheter shaft at a first position,wherein said first positioning element is configured to abut agastroesophageal junction when placed in a gastric cardia; and an inputport at a second position and in fluid communication with said cathetershaft in order to receive said steam wherein the shaft comprises aplurality of ports through which said steam can be released out of saidshaft and wherein said ports are located between said first position andsecond position. The device further comprises a temperature sensorwherein said temperature sensor is used to control the release of saidsteam. The first positioning element comprises at least one of a wiremesh disc, a wire mesh cone, or an inflatable balloon. The firstpositioning element is separated from an ablation region by a distanceof between 0 mm and 1 cm. The diameter of the first positioning elementis between 1 mm and 100 mm.

In another embodiment, the present specification is directed to a deviceto perform ablation of gastrointestinal tissue, comprising a catheterhaving a hollow shaft through which steam can be transported; a firstpositioning element attached to said catheter shaft at a first position,wherein said first positioning element is configured to abut thegastrointestinal tissue; and an input port at a second position and influid communication with said catheter shaft in order to receive saidsteam wherein the shaft comprises one or more ports through which saidsteam can be released out of said shaft onto the gastrointestinaltissue.

Optionally, the device further comprises a temperature sensor whereinsaid temperature sensor is used to control the release of said steam.The first positioning element comprises at least one of a wire mesh discand a wire mesh cone. The diameter of the first positioning element is0.1 mm to 50 mm. The device is used to perform non-circumferentialablation.

In another embodiment, the present specification is directed to a deviceto perform ablation of endometrial tissue, comprising a catheter havinga shaft through which an ablative agent can travel; a first positioningelement attached to said catheter shaft at a first position, whereinsaid first positioning element is configured to center said catheter ina center of a cervix; and a shaft comprises a plurality of ports throughwhich said ablative agent can be released out of said shaft.

Optionally, the device further comprises a second positioning elementattached to said catheter shaft at a second position. The firstpositioning element is conical. The first positioning element comprisesan insulated membrane. The insulated membrane is configured to preventan escape of thermal energy through the cervix. The second positioningelement is disc shaped. The second positioning element has a predefineddimension and wherein said dimension is used to determine a uterinecavity size. The second positioning element has a predefined dimensionand wherein said dimension is used to calculate an amount of thermalenergy needed to ablate the endometrial tissue. The device furthercomprises at least one temperature sensor wherein said temperaturesensor is used to control delivery of said ablative agent. The ablativeagent is steam. The first positioning element is a covered wire mesh.The first positioning element comprises a circular body with a diameterbetween 0.01 mm and 10 cm. The second positioning element is oval andwherein said oval has a long axis between 0.01 mm and 10 cm and a shortaxis between 0.01 mm and 5 cm. When deployed, the positioning elementsalso serve to open up the uterine cavity.

In another embodiment, the present specification is directed toward adevice to perform ablation of endometrial tissue, comprising a catheterhaving a hollow shaft through which steam can be delivered; a firstpositioning element attached to said catheter shaft at a first position,wherein said first positioning element is conical and configured tocenter said catheter in a center of a cervix; a second positioningelement attached to said catheter shaft at a second position, whereinthe second positioning element is elliptical shaped; a plurality ofports integrally formed in said catheter shaft, wherein steam can bereleased out of said ports and directed toward endometrial tissue andwherein said ports are located between said first position and secondposition; and at least one temperature sensor.

Optionally, the second positioning element has a predefined dimensionand wherein said dimension is used to determine a uterine cavity size.The second positioning element has a diameter and wherein said diameteris used to calculate an amount of thermal energy needed to ablate theendometrial tissue. The temperature sensors are used to control deliveryof said ablative agent. The first positioning element comprises wiremesh. The second positioning element has a disc shape that is oval andwherein said oval has a long axis between 0.01 mm and 10 cm and a shortaxis between 0.01 mm and 5 cm.

Optionally, the second positioning element can use one or more sourcesof infrared, electromagnetic, acoustic or radiofrequency energy tomeasure the dimensions of the hollow cavity. The energy is emitted fromthe sensor and is reflected back to the detector in the sensor. Thereflected data is used to determine the dimension of the hollow cavity.

In one embodiment, the present specification discloses a device to beused in conjunction with a tissue ablation system, comprising: a handlewith a pressure-resistant port on its distal end, a flow channel throughwhich an ablative agent can travel, and one or more connection ports onits proximal end for the inlet of said ablative agent and for an RFfeed; an insulated catheter that attaches to said pressure-resistantport of said snare handle, containing a shaft through which an ablativeagent can travel and one or more ports along its length for the releaseof said ablative agent; and one or more positioning elements attached tosaid catheter shaft at one or more separate positions, wherein saidpositioning element(s) is configured to position said catheter at apredefined distance from the tissue to be ablated.

Optionally, the handle has one pressure-resistant port for theattachment of both an ablative agent inlet and an RF feed. The handlehas one separate pressure-resistant port for the attachment of anablative agent inlet and one separate port for the attachment of an RFfeed or an electrical feed.

In another embodiment, the present specification discloses a device tobe used in conjunction with a tissue ablation system, comprising: ahandle with a pressure-resistant port on its distal end, a flow channelpassing through said handle which is continuous with a pre-attached cordthrough which an ablative agent can travel, and a connection port on itsproximal end for an RF feed or an electrical field; an insulatedcatheter that attaches to said pressure-resistant port of said handle,containing a shaft through which an ablative agent can travel and one ormore ports along its length for the release of said ablative agent; andone or more positioning elements attached to said catheter shaft at oneor more separate positions, wherein said positioning element(s) isconfigured to position said catheter at a predefined distance from thetissue to be ablated. Optionally, the distal end of said catheter isdesigned to puncture the target.

In another embodiment, the present specification discloses a device tobe used in conjunction with a tissue ablation system, comprising: anesophageal probe with a pressure-resistant port on its distal end, aflow channel through which an ablative agent can travel, and one or moreconnection ports on its proximal end for the inlet of said ablativeagent and for an RF feed or an electrical feed; an insulated catheterthat attaches to said pressure-resistant port of said esophageal probe,containing a shaft through which an ablative agent can travel and one ormore ports along its length for the release of said ablative agent; andone or more inflatable positioning balloons at either end of saidcatheter positioned beyond said one or more ports, wherein saidpositioning balloons are configured to position said catheter at apredefined distance from the tissue to be ablated.

Optionally, the catheter is dual lumen, wherein a first lumenfacilitates the transfer of ablative agent and a second lumen containsan electrode for RF ablation. The catheter has differential insulationalong its length.

The present specification is also directed toward a tissue ablationdevice, comprising: a liquid reservoir, wherein said reservoir includesan outlet connector that can resist at least 1 atm of pressure for theattachment of a reusable cord; a heating component comprising: a lengthof coiled tubing contained within a heating element, wherein activationof said heating element causes said coiled tubing to increase from afirst temperature to a second temperature and wherein said increasecauses a conversion of liquid within said coiled tubing to vapor; and aninlet connected to said coiled tubing; an outlet connected to saidcoiled tubing; and at least one pressure-resistant connection attachedto the inlet and/or outlet; a cord connecting the outlet of saidreservoir to the inlet of the heating component; a single use cordconnecting a pressure-resistant inlet port of a vapor based ablationdevice to the outlet of said heating component.

In one embodiment, the liquid reservoir is integrated within anoperating room equipment generator. In one embodiment, the liquid iswater and the vapor is steam.

In one embodiment, the pressure-resistant connections are luer lockconnections. In one embodiment, the coiled tubing is copper.

In one embodiment, the tissue ablation device further comprises a footpedal, wherein only when said foot pedal is pressed, vapor is generatedand passed into said single use cord. In another embodiment, only whenpressure is removed from said foot pedal, vapor is generated and passedinto said single use cord.

In another embodiment, the present specification discloses a vaporablation system used for supplying vapor to an ablation device,comprising; a single use sterile fluid container with attachedcompressible tubing used to connect the fluid source to a heating unitin the handle of a vapor ablation catheter. The tubing passes through apump that delivers the fluid into the heating unit at a predeterminedspeed. There is present a mechanism such as a unidirectional valvebetween the fluid container and the heating unit to prevent the backflowof vapor from the heating unit. The heating unit is connected to theablation catheter to deliver the vapor from the heating unit to theablation site. The flow of vapor is controlled by a microprocessor. Themicroprocessor uses a pre-programmed algorithm in an open-loop system oruses information from one or more sensors incorporated in the ablationsystem in a closed-loop system or both to control delivery of vapor.

In one embodiment, the handle of the ablation device is made of athermally insulating material to prevent thermal injury to the operator.The heating unit is enclosed in the handle. The handle locks into thechannel of an endoscope after the catheter is passed through the channelof the endoscope. The operator can than manipulate the catheter byholding the insulated handle or by manipulating the catheter proximal tothe insulating handle.

The present specification is also directed toward a vapor ablationsystem comprising: a container with a sterile liquid therein; a pump influid communication with said container; a first filter disposed betweenand in fluid communication with said container and said pump; a heatingcomponent in fluid communication with said pump; a valve disposedbetween and in fluid communication with said pump and heating container;a catheter in fluid communication with said heating component, saidcatheter comprising at least one opening at its operational end; and, amicroprocessor in operable communication with said pump and said heatingcomponent, wherein said microprocessor controls the pump to control aflow rate of the liquid from said container, through said first filter,through said pump, and into said heating component, wherein said liquidis converted into vapor via the transfer of heat from said heatingcomponent to said fluid, wherein said conversion of said fluid into saidvapor results is a volume expansion and a rise in pressure where saidrise in pressure forces said vapor into said catheter and out said atleast one opening, and wherein a temperature of said heating componentis controlled by said microprocessor.

In one embodiment, the vapor ablation system further comprises at leastone sensor on said catheter, wherein information obtained by said sensoris transmitted to said microprocessor, and wherein said information isused by said microprocessor to regulate said pump and said heatingcomponent and thereby regulate vapor flow. In one embodiment, the atleast one sensor includes one or more of a temperature sensor, flowsensor, or pressure sensor.

In one embodiment, the vapor ablation system further comprises a screwcap on said liquid container and a puncture needle on said first filter,wherein said screw cap is punctured by said puncture needle to providefluid communication between said container and said first filter.

In one embodiment, the liquid container and catheter are disposable andconfigured for a single use.

In one embodiment, the fluid container, first filter, pump, heatingcomponent, and catheter are connected by sterile tubing and theconnections between said pump and said heating component and saidheating component and said catheter are pressure resistant.

The present specification is also directed toward a tissue ablationsystem comprising: a catheter with a proximal end and a distal end and alumen therebetween, said catheter comprising: a handle proximate theproximal end of said catheter and housing a fluid heating chamber and aheating element enveloping said chamber, a wire extending distally fromsaid heating element and leading to a controller; an insulating sheathextending and covering the length of said catheter and disposed betweensaid handle and said heating element at said distal end of saidcatheter; and, at least one opening proximate the distal end of saidcatheter for the passage of vapor; and, a controller operably connectedto said heating element via said wire, wherein said controller iscapable of modulating energy supplied to said heating element andfurther wherein said controller is capable of adjusting a flow rate ofliquid supplied to said catheter; wherein liquid is supplied to saidheating chamber and then converted to vapor within said heating chamberby a transfer of heat from said heating element to said chamber, whereinsaid conversion of said liquid to vapor results in a volume expansionand a rise in pressure within said catheter, and wherein said rise inpressure pushes said vapor through said catheter and out said at leastone opening.

In one embodiment, the tissue ablation system further comprises apressure resistant fitting attached to the fluid supply and a one-wayvalve in said pressure resistant fitting to prevent a backflow of vaporinto the fluid supply.

In one embodiment, the tissue ablation system further comprises at leastone sensor on said catheter, wherein information obtained by said sensoris transmitted to said microprocessor, and wherein said information isused by said microprocessor to regulate said pump and said heatingcomponent and thereby regulate vapor flow.

In one embodiment, the tissue ablation system further comprises a metalframe within said catheter, wherein said metal frame is in thermalcontact with said heating chamber and conducts heat to said catheterlumen, thereby preventing condensation of said vapor. In variousembodiments, the metal frame comprises a metal skeleton with outwardlyextending fins at regularly spaced intervals, a metal spiral, or a metalmesh and the metal frame comprises at least one of copper, stainlesssteel, or another ferric material.

In one embodiment, the heating element comprises a heating block,wherein said heating block is supplied power by said controller.

In various embodiments, the heating element uses one of magneticinduction, microwave, high intensity focused ultrasound, or infraredenergy to heat said heating chamber and the fluid therein.

The present specification also discloses an ablation catheter for usewith a hollow tissue or organ, comprising: a distal end having at leastone opening for the injection of a conductive medium into said hollowtissue or organ and at least one opening for the delivery of an ablativeagent into said hollow tissue or organ; a proximal end configured toreceive said conductive medium and said ablative agent from a source;and, a shaft, having at least one lumen therewithin, between said distalend and said proximal end.

In one embodiment, the ablation catheter for use with a hollow tissue ororgan further comprises at least one positioning element for positioningsaid catheter proximate target tissue to be ablated. In one embodiment,the ablation catheter further comprises at least one occlusive elementto occlude blood flow in said hollow tissue or organ.

The present specification also discloses a method of treating a disorderof a prostate, the method comprising: introducing an ablation catheterinto the prostate; and, delivering an ablative agent into the prostateand ablating prostate tissue without ablating the prostatic urethra. Inone embodiment, the ablative agent is vapor. In one embodiment, thecatheter is introduced transurethrally. In another embodiment, thecatheter is introduced transrectally.

The present specification also discloses an ablation catheter for use intreating a disorder of the prostate, said catheter comprising: one ormore needles for piercing the prostatic tissue and delivering anablative agent into the prostate; and, one or more positioning elementsto position said needles at a predefined distance in the prostate. Inone embodiment, the ablation catheter further comprises a mechanism tocool a prostatic urethra or a rectal wall.

The present specification also discloses a method for treating benignprostatic hyperplasia of a prostate of a patient comprising the stepsof: inserting a plurality of vapor delivery needles through a urethralwall of the patient in a plurality of locations into a prostate lobe;and, delivering water vapor through the needles into the prostate ateach location to ablate the prostatic tissue.

The present specification also discloses a method of providing ablationto a patient's endometrium comprising the steps of: inserting anablation catheter, said catheter comprising a lumen and vapor deliveryports, through a cervix and a cervical canal into the endometrialcavity; and, delivering an ablative agent through said ablation catheterlumen and said delivery ports and into the endometrial cavity to createendometrial ablation. In one embodiment, the method of providingablation to a patient's endometrium further comprises the step ofmeasuring at least one dimension of the endometrial cavity and usingsaid dimension to determine the delivery of ablative agent. In oneembodiment, the method of providing ablation to a patient's endometriumfurther comprises the step of using a positioning element to positionsaid catheter in the center of the endometrial cavity. In oneembodiment, the positioning element includes an expansion mechanism incontact with endometrial tissue to move said endometrial tissue surfacesaway from the vapor delivery ports of the catheter. In one embodiment,the method of providing ablation to a patient's endometrium furthercomprises the step of using an occlusive element to occlude the cervicalos to prevent leakage of the ablative agent through the os. In oneembodiment, the ablative agent heats and expands the air in theendometrial cavity, expanding the endometrial cavity to allow for moreuniform delivery of ablative agent. As the endometrial cavity isexpanded, the pressure therein is maintained at a level such that theablative agent does not escape the endometrial cavity.

The present specification also discloses a method of providing ablativetherapy to a patient's endometrium comprising the steps of: inserting acoaxial vapor ablation catheter, comprising an inner catheter and anouter catheter, through the cervical os and into the cervical canal toocclude the cervical canal; advancing the inner catheter of the coaxialvapor ablation catheter into the endometrial cavity; and, deliveringvapor through vapor delivery ports on the inner catheter into theendometrial cavity to ablate the endometrial tissue. The inner catheteris advanced to the fundus of the uterus, thus measuring the uterinecavity length. The length of inner catheter needed, in-turn determinesthe number of vapor delivery ports that are exposed to deliver theablative agent, thus controlling the amount of ablative agent to bedelivered.

The present specification also discloses a method for hemorrhoidablation comprising the steps of: inserting an ablation device, saiddevice comprising a port for engaging a hemorrhoid, at least one portfor delivery of an ablative agent, and a mechanism to create suction,into a patient's anal canal; engaging the targeted hemorrhoid bysuctioning the hemorrhoid into the ablation device; and, delivering theablative agent to the hemorrhoid to ablate the hemorrhoid. In oneembodiment, the method further comprises the step of compressing theengaged hemorrhoid prior to delivering the ablative agent.

The present specification also discloses a method of ablating a tissueor organ, comprising the steps of: inserting a catheter into said targettissue or organ; using the catheter to remove contents of said targettissue or organ via suction; using the catheter to replace said removedcontents with a conductive medium; introducing an ablative agent to saidconductive medium, and changing the temperature of said conductivemedium to ablate said tissue or organ.

The present specification also discloses a method of ablating a hollowtissue or organ, comprising the steps of: inserting a catheter into ahollow tissue or organ of a patient, said catheter having a stentcoupled to its distal end; advancing said catheter and stent to targettissue; deploying said stent, wherein said deployment involves releasingsaid stent from said distal end of said catheter, further wherein saiddeployment causes said stent to expand such that it comes into physicalcontact with, and is held in place by, the internal surface of saidhollow tissue or organ; and, delivering ablative agent through saidcatheter and into the lumen of said stent, wherein ablative energy fromsaid ablative agent is transferred from said lumen through said stentand into the surrounding tissue to ablate said tissue. In oneembodiment, the stent is optionally covered by a thermally permeablemembrane which allows for the ablative energy to pass from inside of thestent to the surrounding tissue while preventing leakage of asignificant amount of fluid from inside the stent into the surroundingtissue. In one embodiment, the membrane also prevents ingrowth of tumortissue into the stent.

The present specification also discloses a stent for use with anablation catheter, said stent comprising: a compressible, cylindricalhollow body with a lumen therewithin, said body being comprised of athermally conductive material, wherein said body is transformablebetween a first, compressed configuration for delivery and a second,expanded configuration for deployment; one or more openings for thepassage of thermal energy from said lumen of said stent to the exteriorof said stent; one or more flaps covering said openings to prevent theingrowth of tissue surrounding said stent into the lumen of said stent;and, at least one coupling means to couple said stent to said ablationcatheter for delivery and/or retrieval. In one embodiment, thedeployment of the stent and delivery of ablative energy can be performedin separate steps and at separate times. For example, the ablation canbe performed at a future time after the placement of the stent to shrinkthe growth of an expanding tumor. Multiple serial ablations can beperformed through the same stent over time.

The present specification also discloses an ablation catheter assemblycomprising: a catheter having an elongate body with a lumen within, aproximal end, and a distal end; a first inline chamber having anelongate body with a lumen within, a proximal end, and a distal end,wherein said distal end of said first inline chamber is connected tosaid proximal end of said catheter and said lumen of said first inlinechamber is in fluid communication with said lumen of said catheter,further wherein said first inline chamber is composed of a ferromagneticor thermally conducting material; a second inline chamber having anelongate body with a lumen within, a proximal end, and a distal end,wherein said distal end of said second inline chamber is connected tosaid proximal end of said first inline chamber and said lumen of saidsecond inline chamber is in fluid communication with said lumen of saidfirst inline chamber, further wherein said second inline chamber isconfigured to contain a fluid; an optional one way valve positioned atthe connection between said first inline chamber and said second inlinechamber, said valve allowing flow of fluid from said second inlinechamber into said first inline chamber but not in the reverse direction;and, a piston within and proximate said proximal end of said secondinline chamber; wherein said proximal end of said second inline chamberis connected to an external pump and said pump engages said piston topush a fluid from said second inline chamber into said first inlinechamber where an external heating element heats said first inlinechamber and the transfer of said heat to said fluid causes vaporizationof said fluid, further wherein said vaporized fluid passes through saidelongate body and out said distal end of said catheter.

Optionally, in one embodiment, the ablation catheter assembly furthercomprises a thermally insulated handle on said catheter body. In oneembodiment, the pump is a syringe pump. In one embodiment, the pump iscontrolled by a microprocessor to deliver ablative vapor at apredetermined rate. Optionally, a peristaltic pump or any other pumpknown in the field can be used to push fluid from the second inlinechamber to the first inline chamber at a rate that is controllable by amicroprocessor. In one embodiment, the ablation catheter assemblyfurther comprises at least one sensor on said catheter, whereininformation from said sensor is relayed to said microprocessor and thedelivery rate of ablative vapor is based upon said information.

In one embodiment, a membrane is positioned between the first inlinechamber and the second inline chamber which functions to prevent flow ofthe fluid from the second inline chamber into the first inline chamberuntil therapy is ready to be delivered. As pressure is applied to thefluid in the second inline chamber by action of the piston, saidpressure is transmitted to the membrane, resulting in rupture of themembrane. The fluid is then allowed to flow from the second inlinechamber into the first inline chamber.

In another embodiment, a valve is positioned between the first inlinechamber and the second inline chamber which functions to prevent flow ofthe fluid from the second inline chamber into the first inline chamberuntil therapy is ready to be delivered. As pressure is applied to thefluid in the second inline chamber by action of the piston, saidpressure is transmitted to the valve, resulting in opening of the valve.The fluid is then allowed to flow from the second inline chamber intothe first inline chamber.

In another embodiment, a heat sensitive plug is positioned between thefirst inline chamber and the second inline chamber which functions toprevent flow of the fluid from the second inline chamber into the firstinline chamber until therapy is ready to be delivered. As thetemperature in the first inline chamber rises above a predeterminedlevel, the plug melts and the fluid is allowed to flow from the secondinline chamber into the first inline chamber.

In another embodiment, a shape-memory metal member is positioned betweenthe first inline chamber and the second inline chamber which functionsto prevent flow of the fluid from the second inline chamber into thefirst inline chamber until therapy is ready to be delivered. As thetemperature in the first inline chamber rises above a predeterminedlevel, the shape-memory metal member changes in shape to provide apathway such that fluid is allowed to flow from the second inlinechamber into the first inline chamber.

In one embodiment, the heating element is any one of a resistive heater,an RF heater, a microwave heater and an electromagnetic heater. In oneembodiment, the fluid is water. In one embodiment, the first inlinechamber comprises a plurality of channels within to increase the contactsurface area of said fluid with said first inline chamber. In variousembodiments, the channels comprise any one of metal tubes, metal beads,and metal filings.

In one embodiment, the elongate body of said catheter includes an outersurface and an inner surface and said inner surface includes a groovepattern to decrease the resistance to flow of said fluid within saidcatheter.

Optionally, in one embodiment, the catheter comprises a first inner walland a second outer wall and an insulating layer between said first walland said second wall. In one embodiment, said first inner wall and saidsecond outer wall are connected by a plurality of spokes. In oneembodiment, the insulating layer is filled with air. In anotherembodiment, the insulating layer is filled with a fluid. In anotherembodiment, the insulating layer is made of any thermally insulatingmaterial.

The present specification also discloses a system for heating a fluid,said system comprising: a chamber for containing said fluid, saidchamber defining an enclosed three dimensional space and having aproximal end and a distal end, wherein said proximal end includes aninlet port for delivery of said fluid and said distal end includes anoutlet port, further wherein said chamber is composed of an electricallynon-conducting and thermally insulating material and an inductionheating element made of a ferromagnetic material positioned within saidchamber; and, an induction coil positioned around said chamber, saidinduction heating element capable of absorbing the energy of a magneticfield induced by an alternating current; wherein, when the alternatingcurrent is supplied to said induction coil, a magnetic field is createdin the area surrounding said chamber and said magnetic field induceselectric current flow within the ferromagnetic material of said chamber,further wherein said magnetic field induces magnetization of saidferromagnetic material which undergoes a magnetic hysteresis, resultingin hysteresis loss and subsequent further heating of said ferromagneticmaterial, further wherein said electric current flow results in theresistive heating of said chamber and said heat is transferred to saidfluid, converting said fluid into vapor which exits said chamber throughsaid outlet port.

In various embodiments, the ferromagnetic material comprises any one of,or alloys of, iron, nickel, stainless steel, manganese, silicon, carbonand copper. In various embodiments, the ferromagnetic material is acurie material with a curie temperature between 60° C. and 250° C.

In one embodiment, the induction coil comprises a metal wire coil loopedabout said chamber. In one embodiment, the coil is looped about a lengthof said chamber such that said coil is in physical contact with saidchamber. In other embodiments, the coil is looped about a length of saidchamber spaced away from said chamber with a layer of air or insulatingmaterial between said coil and said chamber.

The present specification also discloses a method for heating a fluid,said method comprising the steps of: providing a chamber for containingsaid fluid, said chamber defining an enclosed three dimensional spaceand having a proximal end and a distal end, wherein said proximal endincludes an inlet port for delivery of said fluid and said distal endincludes an outlet port, further wherein said chamber is composed of anelectrically non-conducting and thermally insulating material and aninduction heating element made of a ferromagnetic material positionedwithin said chamber; surrounding said chamber with an induction coil;filling said container with said fluid; providing an alternating currentto said induction coil such that a magnetic field is created in the areasurrounding said chamber and said magnetic field induces electriccurrent flow within the ferromagnetic material of said chamber, furtherwherein said magnetic field induces magnetization of said ferromagneticmaterial which undergoes a magnetic hysteresis, resulting in hysteresisloss and subsequent further heating of said ferromagnetic material,further wherein said electric current flow results in the resistiveheating of said chamber and said heat is transferred to said fluid,converting said fluid into vapor which exits said chamber through saidoutlet port. Optionally, the chamber is insulated to prevent heat lossesfrom the chamber or thermal injury to an operator from the heatedchamber.

The present specification also discloses a system for heating a fluid,said system comprising: a chamber for containing said fluid, saidchamber defining an enclosed three dimensional space and having aproximal end and a distal end, wherein said proximal end includes aninlet port for delivery of said fluid and said distal end includes anoutlet port, further wherein said chamber is composed of an electricallynon-conducting and thermally insulating material and an inductionheating element made of a Curie point material positioned within saidchamber; and, an induction coil positioned around said chamber, saidinduction coil capable of receiving high frequency energy; wherein, whenhigh frequency energy is supplied to said induction coil, a magneticfield is created in the area surrounding said chamber and said magneticfield induces electric current flow within the Curie material of saidchamber, further wherein said magnetic field induces magnetization ofsaid ferromagnetic material which undergoes a magnetic hysteresis,resulting in hysteresis loss and subsequent further heating of saidferromagnetic material, further wherein said electric current flowresults in the resistive heating of said chamber and said heat istransferred to said fluid, converting said fluid into vapor which exitssaid chamber through said outlet port, further wherein when said Curiepoint material is heated to its Curie temperature, it temporarily losesits ferromagnetic properties, ceases to absorb energy through magnetichysteresis loss and the temperature drops below its Curie temperature,has its ferromagnetic properties restored and once again undergoeshysteresis and generates heat, and continues in a cyclical process aslong as said high frequency energy is supplied to said induction coil.Optionally, the chamber is insulated to prevent heat losses from thechamber or thermal injury to an operator from the heated chamber.

The present specification also discloses a vapor ablation systemcomprising: a chamber for containing a fluid, said chamber defining anenclosed three dimensional space and having a proximal end and a distalend, wherein said proximal end includes an inlet port for delivery ofsaid fluid and said distal end includes an outlet port, further whereinsaid chamber is composed of an electrically non-conducting and thermallyinsulating material and an induction heating element made of a Curiepoint material positioned within said chamber; a catheter connected tosaid outlet port of said chamber; a fluid supply source connected tosaid inlet port of said chamber; and, an induction coil positionedaround said chamber, said induction coil capable of receiving highfrequency energy; wherein, when high frequency energy is supplied tosaid induction coil, a magnetic field is created in the area surroundingsaid chamber and further wherein said magnetic field inducesmagnetization of said ferromagnetic material which undergoes a magnetichysteresis, resulting in hysteresis loss and subsequent further heatingof said ferromagnetic material and said magnetic field induces electriccurrent flow within the Curie material of said chamber, further whereinsaid electric current flow results in the resistive heating of saidchamber and said heat is transferred to said fluid, converting saidfluid into vapor which exits said chamber through said outlet port andenters said catheter for vapor delivery, further wherein when said Curiepoint material is heated to its Curie temperature, it temporarily losesits ferromagnetic properties and energy absorption through magnetichysteresis loss ceases, the temperature drops below its Curietemperature and its ferromagnetic properties are restored and it onceagain undergoes hysteresis and generates heat, and continues in acyclical process as long as said high frequency energy is supplied tosaid induction coil.

The Curie point material may have a Curie temperature ranging from 60 to500 degrees Celsius. Optionally, the Curie point material is anickel/iron alloy comprising at least 25% nickel.

The Curie point material may further comprise any one or combination ofcopper, chromium, manganese, and silicon.

Optionally, the fluid is water and said vapor is steam.

The vapor ablation system may further comprise a fluid pump. Optionally,the fluid pump is a syringe pump.

The vapor ablation system may further comprise a microcontroller tocontrol the delivery of said vapor. Optionally, the vapor ablationsystem further comprises a touchscreen user interface enabling controlof system parameters including power, vapor flow rate, and pressure.Optionally, the vapor ablation system further comprises a multi-functionfoot pedal. Optionally, the vapor ablation system further comprises atleast one sensor wherein information from said sensor is relayed to saidmicrocontroller and a delivery rate of said vapor is based upon saidinformation. The sensor may include any one or combination of atemperature sensor, pressure sensor, or impedance tuner. Optionally, thevapor ablation system further comprises at least one alarm wherein saidalarm is issued when information from said at least one sensor fallsoutside of a predetermined threshold value.

The chamber may be tightly packed with ball bearings balls composed ofsaid Curie point material and said fluid physically contacts said ballbearings balls during heat transfer.

The chamber may be single use and disposable.

Optionally, the chamber has a clam shell shape and said fluid does notphysically contact said Curie point material.

Optionally, the chamber is reusable.

The chamber and catheter may be thermally insulated.

The present specification also discloses a method for heating a fluid,said method comprising the steps of: providing a chamber for containingsaid fluid, said chamber defining an enclosed three dimensional spaceand having a proximal end and a distal end, wherein said proximal endincludes an inlet port for delivery of said fluid and said distal endincludes an outlet port, further wherein said chamber is composed of anelectrically non-conducting and thermally insulating material and aninduction heating element made of a Curie point material positionedwithin said chamber; surrounding said chamber with an induction coil;providing high frequency energy to said induction coil such that amagnetic field is created in the area surrounding said chamber and saidmagnetic field induces magnetization of said ferromagnetic materialwhich undergoes magnetic hysteresis resulting in hysteresis loss andsubsequent heating of said ferromagnetic material and additionallyinduces electric current flow within the Curie point material of saidchamber, inducing eddy currents and resulting in the generation ofadditional heat within said chamber; filling said container with saidfluid, wherein said heat is transferred to said fluid, converting saidfluid into vapor which exits said chamber through said outlet port;continuing to supply said high frequency energy such that said Curiepoint material is heated to its Curie temperature, temporarily loses itsferromagnetic properties, whereupon the energy absorption throughhysteresis loss ceases, the temperature drops below its Curietemperature whereupon the Curie point material's ferromagneticproperties are restored and it once again undergoes hysteresis andgenerates heat, and continues in a cyclical process as long as said highfrequency energy is supplied to said induction coil.

The present specification also discloses a vapor generation systemcomprising: a vaporizer for vaporizing a liquid to form a vapor, thevaporizer including: a means for generating a changing magnetic field; anon-ferromagnetic chamber having an inlet and an outlet and capable ofwithstanding a pressure of at least 5 psi, said means for generating achanging magnetic field positioned about said chamber; and aferromagnetic member contained within said non-ferromagnetic chambercreating a passage defined by the space between an outer surface of theferromagnetic member and an inner surface of the chamber, saidferromagnetic member comprising a thermal mass and a surface area beingdefined around the member and the non-ferromagnetic chamber, whereinsaid ferromagnetic member becomes inductively heated by the changingmagnetic field to a temperature sufficient to convert liquid flowingthrough the passage to vapor and an inner surface of the chamber isnon-inductively heated by the member to a temperature sufficient toallow said conversion of said liquid to vapor while a temperature of anouter surface of the chamber is actively maintained below 100° C., and acatheter connected to the outlet of the chamber for supplying the vaporformed within the passage to a defined region in the body.

Optionally, the outer surface of the chamber is actively cooled tomaintain a temperature of the outer surface to be at least 20° C. lessthan a temperature of the inner surface of the chamber.

Optionally, a surface area to volume ratio of the ferromagnetic memberis equal to or greater than 2(D₁+L)/D₂×L where D₁ is the shortestcross-sectional dimension of the member, D₂ is the longestcross-sectional dimension of the member and L is the length of themember.

The passage may have a width equal to or less than 25 mm.

Optionally, the non-ferromagnetic chamber is composed of thermoplasticor ceramic.

Optionally, the ceramic is a machinable glass ceramic such as MACOR®.

The means for generating a magnetic field may be an inductive coil.Optionally, the inductive coil is separated from said outer surface ofsaid chamber by at least 0.1 mm. Optionally, a cooling agent is passedbetween said coil and said outer surface of said chamber to maintain atemperature of said outer surface at less than 100° C. Optionally, atemperature of the outer surface of the chamber is maintained to be atleast 20° C. less than a temperature of the inner surface of thechamber.

The present specification also discloses a vapor generation cathetercomprising: a liquid source; a vaporizer in fluid connection with saidliquid source for vaporizing the liquid to form a vapor, the vaporizercomprising: a means for generating a changing magnetic field, athermally insulating chamber having an inlet and an outlet and capableof withstanding a pressure greater than 5 psi, said means for generatinga changing magnetic field positioned about said chamber; a ferromagneticmember contained within said chamber creating a passage defined by thespace between an outer surface of the ferromagnetic member and an innersurface of the chamber, wherein said ferromagnetic member is inductivelyheated by the changing magnetic field and said chamber isnon-inductively heated by the member, said ferromagnetic member andchamber collectively supplying sufficient heat to a liquid in saidpassage to convert the liquid into vapor; and a resistive valve at theoutlet of the chamber that opens at a pressure of less than 5 psi; and acatheter in fluid connection with the resistive valve for supplying thevapor to the targeted tissue.

Optionally, the liquid is non-ionized water or a solution of a metalsalt and water.

The present specification also discloses a method of ablating a tissue,the method comprising: passing a liquid through a passage in a thermallyinsulating chamber containing a ferromagnetic member within at a flowrate between 0.1 ml/min to 100 ml/min, wherein said passage is definedby the space between an outer surface of the ferromagnetic member and aninner surface of the thermally insulating chamber and a distance betweenthe two surfaces is equal to or less than 25 mm; inductively heating theferromagnetic member to a predefined temperature equal to or greaterthan 100° C.; and non-inductively heating the chamber wherein thetemperature of an outer surface of the chamber is maintained at lessthan 100° C.; wherein the inductively heated ferromagnetic member andnon-inductively heated chamber vaporize the liquid within the passage,causing an increase in a pressure inside the passage to greater than 1psi but less than 100 psi such that created vapor flows out of thepassage through a catheter to a defined area for ablation.

Optionally, the ferromagnetic member comprises a Curie point material.

Optionally, the chamber includes a pressure sensor which senses thepressure in the chamber and said method further comprises the step ofshutting down said inductive heating when a predefined pressure isreached. Optionally, the pressure sensor is in line with the path of thefluid and senses the pressure in the path of the fluid and said methodfurther comprises the step of shutting down said inductive heating whena predefined pressure is reached.

Optionally, the chamber includes a temperature sensor which senses thetemperature of the outer surface of the chamber and said method furthercomprises the step of shutting down said inductive heating when apredefined temperature is reached.

Optionally, the chamber includes a system to actively cool down saidouter surface of the chamber and said method further comprises the stepof activating said system to maintain a temperature of said outersurface at less than 100° C. Optionally, a temperature of the outersurface of the chamber is maintained to be at least 20° C. less than atemperature of the inner surface of the chamber.

Optionally, the chamber includes a valve at an outlet of said passageand said valve opens at a pressure equal to or less than 5 psi.

Optionally, the chamber includes a valve at an inlet of said passagewhich allows backflow of a liquid at a pressure greater than 5 psi.

The present specification also discloses a steam-based ablation systemcomprising: a disposable fluid circuit comprising: a water reservoircontaining water; a water heating chamber having a length, wherein thewater heating chamber comprises a non-ferromagnetic material having alumen extending therethrough and a ferromagnetic material positionedwithin said lumen and wherein the ferromagnetic material is separatedfrom the non-ferromagnetic material, across the length of the waterheating chamber, by a space; a catheter comprising a proximal end and adistal end, wherein the distal end comprises one or more ports; and acontiguous fluid channel connecting said water reservoir, said waterheating chamber, and the proximal end of said catheter; an inductionchamber adapted to receive said water heating chamber, wherein saidinduction chamber comprises a plurality of coils for receiving anelectrical current and for generating a magnetic field; an inductioncircuit for delivering said electrical current to said inductionchamber; and a pump or motor for applying a force to said water in thewater reservoir in order to move the water from the water reservoir andinto the water heating chamber.

Optionally, the system further comprises mechanisms to keep the water inthe reservoir separate from the water heating chamber until therapy isinitiated. These mechanisms may include one of a pressure sensitivemembrane that bursts when a certain amount of pressure is applied, athermally sensitive plug that dissolves when a certain temperature isexceeded, or a valve with a valve stem actuated by pressure (against aspring) or temperature (shape-memory metal or bi-metal).

The induction circuit may generate a sinusoidal wave form and comprise aswitching circuit having a resonant tank circuit.

Optionally, the non-ferromagnetic material is electrically insulating.Optionally, during operation, a lumen surface of the non-ferromagneticmaterial is configured to be heated to a temperature greater than 100degrees Celsius. Optionally, during operation, an external surface ofthe non-ferromagnetic material is configured to be heated to atemperature no greater than 100 degrees Celsius. Optionally, duringoperation, an external surface of the non-ferromagnetic material isconfigured to be heated to a temperature at least 20° C. below atemperature of an inner surface of the non-ferromagnetic material.Optionally, during operation, an external surface of thenon-ferromagnetic material is configured to be cooled to a temperatureat least 20° C. below a temperature of an inner surface of thenon-ferromagnetic material. Optionally, during operation, the system isprogrammed to shut down heating when an external surface of thenon-ferromagnetic material is heated to a temperature greater than 100degrees Celsius.

The induction chamber may comprise a cylindrical volume around whichsaid plurality of coils are positioned and a lumen positioned withinsaid cylindrical volume adapted to receive said water heating chamber.

Optionally, said water is at least one of ionized water, non-ionizedwater, sterile water, or a solution of metal salt and water.

The electrical current may have a frequency of between 100 Hz and 100kHz.

Optionally, during operation, the water heating chamber and inductionchamber are magnetically coupled wherein a conversion of magnetic energyinto heat within the water heating chamber has an efficiency of greaterthan 40%.

The non-ferromagnetic material may be a cylinder and the ferromagneticmaterial may be a metal rod.

The ferromagnetic material may comprise any one of, or alloys of, iron,nickel, stainless steel, manganese, silicon, carbon, copper,electrically conducting material, electrically insulating material, or aCurie material having a Curie temperature between 60° C. and 500° C.

Optionally, the disposable fluid circuit does not comprise any inputports or openings for receiving fluid from an external source into saiddisposable fluid circuit. Optionally, the disposable fluid circuit doesnot comprise any other ports or openings, other than the one or moreports in the catheter, for receiving or expelling fluid external to saiddisposable fluid circuit.

The fluid channel may comprise flexible tubing wherein the waterreservoir is a pliable plastic bag or a syringe.

Optionally, prior to use, a portion of the fluid channel positionedbetween the water reservoir and the water heating chamber is blocked bya barrier, thereby blocking water from passively flowing from the waterreservoir to the water heating chamber. Optionally, during use, saidbarrier is adapted to be breached by an increase in water pressure topermit water to flow from the water reservoir to the water heatingchamber. Optionally, during use, said barrier is adapted to be breachedby an increase in the temperature to permit water to flow from the waterreservoir to the water heating chamber.

Optionally, the steam-based ablation system further comprises a checkvalve or a fracture diaphragm positioned in the contiguous fluid channelbetween the water reservoir and the water heating chamber to preventwater from entering said water heating chamber until force is applied tosaid water.

Optionally, a temperature of an external surface of said water heatingchamber does not increase by more than 500 percent of its pre-operationexternal surface temperature during five minutes or less of continuousoperation. Continuous operation may be defined as operation during whicha temperature of the ferromagnetic material is maintained at a levelgreater than 100° C.

Optionally, during operation, a temperature of an external surface ofsaid water heating chamber does not exceed 120 degrees Celsius.Optionally, during operation, a temperature of an external surface ofsaid water heating chamber does not exceed 150 degrees Celsius.Optionally, during operation, a temperature profile of the water heatingchamber is measured to identify a maximum temperature and a location ofsaid maximum temperature in said heating chamber.

The steam-based ablation system may further comprise a thermocouplewherein said thermocouple is positioned proximate said location of saidmaximum temperature.

The present specification also discloses a steam-based ablation systemcomprising: a disposable fluid circuit comprising: a water reservoircontaining water; a water heating chamber having a length, wherein thewater heating chamber comprises a volume of non-ferromagnetic materialhaving a lumen extending therethrough and a ferromagnetic cylindricalrod, having a thermal capacity of 0.05 cal/K to 1 Mcal/K, positionedwithin said lumen; a catheter comprising a proximal end and a distalend, wherein the distal end comprises one or more ports; and acontiguous fluid channel connecting said water reservoir, said waterheating chamber, and the proximal end of said catheter; an inductionchamber adapted to receive said water heating chamber, wherein saidinduction chamber comprises a plurality of coils for receiving anelectrical current and for generating a magnetic field; and an inductioncircuit for delivering said electrical current to said inductionchamber.

The steam-based ablation system may further comprise a pump for applyinga force to said water in the water reservoir in order to move the waterfrom the water reservoir, through the water heating chamber, and intothe catheter.

The steam-based ablation system may further comprise a motor forapplying a force to said water in the water reservoir in order to movethe water from the water reservoir, through the water heating chamber,and into the catheter.

The water reservoir may be elevated relative to the water heatingchamber wherein water in said water reservoir is gravity fed into thewater heating chamber.

Optionally, the water reservoir comprises a bladder tank.

The induction chamber may comprise a cylindrical volume around whichsaid plurality of coils are positioned and a lumen positioned withinsaid cylindrical volume adapted to receive said water heating chamber.

Optionally, the disposable fluid circuit does not comprise any ports oropenings, other than the one or more ports in the catheter, forexpelling water out from the disposable fluid circuit or for receivingwater from an external source.

The present specification also discloses a steam-based ablation systemcomprising: a disposable fluid circuit comprising: a pliable plastic bagcontaining water; a water heating chamber having a length, wherein thewater heating chamber comprises a volume of non-ferromagnetic materialhaving a lumen extending therethrough and a ferromagnetic cylindricalrod positioned within said lumen; a catheter comprising a proximal endand a distal end, wherein the distal end comprises one or more ports;and flexible tubing connecting said water reservoir, said water heatingchamber, and the proximal end of said catheter, wherein the disposablefluid circuit does not comprise any ports or openings, other than theone or more ports in the catheter, for expelling water or vapor out fromthe disposable fluid circuit or for receiving water from an externalsource; an induction chamber adapted to receive said water heatingchamber, wherein said induction chamber comprises a plurality of coilsfor receiving an electrical current and for generating a magnetic field;and an induction circuit for delivering said electrical current to saidinduction chamber.

Optionally, the steam-based ablation system further comprises a handleattached to said catheter for manipulating said catheter. Heatingprovided by said water heating chamber does not occur in the handle.Optionally, the steam-based ablation system further comprises anadditional mechanism in a handle or along a length of said catheterdistal to the handle to secondarily heat the vapor.

Optionally, prior to use, a portion of an internal lumen of the flexibletubing positioned between the water reservoir and the water heatingchamber is blocked by a barrier, thereby blocking water from passivelyflowing from the water reservoir to the water heating chamber.

Optionally, the induction chamber comprises a volume around which saidplurality of coils are positioned and a lumen positioned within saidvolume adapted to receive said water heating chamber.

Optionally, the non-ferromagnetic material is a cylinder, theferromagnetic material is a metal rod, and the ferromagnetic materialcomprises any one of, or alloys of, iron, nickel, stainless steel,manganese, silicon, carbon, copper, electrically conducting material,electrically insulating material, or a Curie material having a Curietemperature between 60° C. and 500° C.

The present specification also discloses a vapor ablation systemincluding a catheter component comprising: a water reservoir; a heatingchamber; and a catheter; and a generator component comprising: aninduction coil and a microprocessor, wherein said catheter component isoperationally connected to said generator component such that saidinduction coil can be positioned proximate said heating chamber forinductive heating of water within said heating chamber. Optionally, thecatheter component is a single-use component while the generatorcomponent is a multiple-use component.

The aforementioned and other embodiments of the present invention shallbe described in greater depth in the drawings and detailed descriptionprovided below.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will befurther appreciated, as they become better understood by reference tothe detailed description when considered in connection with theaccompanying drawings, wherein:

FIG. 1A illustrates an ablation device, in accordance with an embodimentof the present specification;

FIG. 1B illustrates another embodiment of a catheter for use with theablation device of FIG. 1A;

FIG. 2A illustrates a longitudinal section of an ablation device withports distributed thereon;

FIG. 2B illustrates a cross section of a port on the ablation device, inaccordance with an embodiment of the present specification;

FIG. 2C illustrates a cross section of a port on the ablation device, inaccordance with another embodiment of the present specification;

FIG. 2D illustrates a catheter of the ablation device, in accordancewith an embodiment of the present specification;

FIG. 2E illustrates a catheter of the ablation device, in accordancewith another embodiment of the present specification;

FIG. 2F illustrates a catheter of the ablation device, in accordancewith yet another embodiment of the present specification;

FIG. 2G is a flow chart listing the steps involved in a hollow tissue ororgan ablation process using an ablation device, in accordance with oneembodiment of the present specification;

FIG. 2H illustrates an ablation device in the form of a catheterextending from a conventional snare handle, in accordance with anembodiment of the present specification;

FIG. 2I illustrates a cross section of an ablation device in the form ofa catheter extending from a conventional snare handle with apre-attached cord, in accordance with another embodiment of the presentspecification;

FIG. 2J illustrates an ablation device in the form of a catheterextending from a conventional esophageal probe, in accordance with anembodiment of the present specification;

FIG. 3A illustrates the ablation device placed in an uppergastrointestinal tract with Barrett's esophagus to selectively ablatethe Barrett's tissue, in accordance with an embodiment of the presentspecification;

FIG. 3B illustrates the ablation device placed in an uppergastrointestinal tract with Barrett's esophagus to selectively ablatethe Barrett's tissue, in accordance with another embodiment of thepresent specification;

FIG. 3C is a flowchart illustrating the basic procedural steps for usingthe ablation device, in accordance with an embodiment of the presentspecification;

FIG. 3D is a flowchart listing the steps of one embodiment of a methodof providing vapor to a hollow organ where the vapor heats the air inthe hollow organ, thus expanding the organ for uniform delivery ofablative energy;

FIG. 3E is a flowchart listing the steps of one embodiment of a methodof providing vapor to a hollow organ wherein the vapor does not escapesubstantially beyond the target tissue to be ablated;

FIG. 3F illustrates an esophageal ablation catheter with venting tubesin accordance with one embodiment of the present specification;

FIG. 3G illustrates an esophageal ablation catheter with a venting tubein accordance with another embodiment of the present specification;

FIG. 4A illustrates the ablation device placed in a colon to ablate aflat colon polyp, in accordance with an embodiment of the presentspecification;

FIG. 4B illustrates the ablation device placed in a colon to ablate aflat colon polyp, in accordance with another embodiment of the presentspecification;

FIG. 4C illustrates an ablation catheter having an ampullary shieldinserted in the duodenum of a patient, in accordance with one embodimentof the present specification;

FIG. 4D is a flowchart listing the steps in one embodiment of a methodof using the ablation catheter having an ampullary shield of FIG. 4C;

FIG. 4E illustrates deflated, lateral inflated, and frontal inflatedviews of an ablation catheter having an insulating membrane for duodenalablation, in accordance with one embodiment of the presentspecification;

FIG. 5A illustrates the ablation device with a coaxial catheter design,in accordance with an embodiment of the present specification;

FIG. 5B illustrates a partially deployed positioning device, inaccordance with an embodiment of the present specification;

FIG. 5C illustrates a completely deployed positioning device, inaccordance with an embodiment of the present specification;

FIG. 5D illustrates the ablation device with a conical positioningelement, in accordance with an embodiment of the present specification;

FIG. 5E illustrates the ablation device with a disc shaped positioningelement, in accordance with an embodiment of the present specification;

FIG. 6 illustrates an upper gastrointestinal tract with a bleedingvascular lesion being treated by the ablation device, in accordance withan embodiment of the present specification;

FIG. 7A illustrates endometrial ablation being performed in a femaleuterus by using the ablation device, in accordance with an embodiment ofthe present specification;

FIG. 7B is an illustration of a coaxial catheter used in endometrialtissue ablation, in accordance with one embodiment of the presentspecification;

FIG. 7C is a flow chart listing the steps involved in an endometrialtissue ablation process using a coaxial ablation catheter, in accordancewith one embodiment of the present specification;

FIG. 7D is an illustration of a bifurcating coaxial catheter used inendometrial tissue ablation, in accordance with one embodiment of thepresent specification;

FIG. 7E is a flowchart listing the steps of a method of using theablation catheter of FIG. 7D to ablate endometrial tissue, in accordancewith one embodiment of the present specification;

FIG. 7F is an illustration of a bifurcating coaxial catheter withexpandable elements used in endometrial tissue ablation, in accordancewith one embodiment of the present specification;

FIG. 7G is an illustration of the catheter of FIG. 7F inserted into apatient's uterine cavity for endometrial tissue ablation, in accordancewith one embodiment of the present specification;

FIG. 7H is a flowchart listing the steps of a method of using theablation catheter of FIG. 7F to ablate endometrial tissue, in accordancewith one embodiment of the present specification;

FIG. 7I is an illustration of a bifurcating coaxial catheter used inendometrial tissue ablation, in accordance with another embodiment ofthe present specification;

FIG. 7J is an illustration of a bifurcating coaxial catheter used inendometrial tissue ablation, in accordance with yet another embodimentof the present specification;

FIG. 7K is an illustration of a water cooled catheter used inendometrial tissue ablation, in accordance with one embodiment of thepresent specification;

FIG. 7L is an illustration of a water cooled catheter used inendometrial tissue ablation and positioned in a uterus of a patient, inaccordance with another embodiment of the present specification;

FIG. 7M is an illustration of a water cooled catheter used in cervicalablation, in accordance with one embodiment of the presentspecification;

FIG. 7N is an illustration of the catheter of FIG. 7M positioned in acervix of a patient;

FIG. 7O is a flowchart listing the steps involved in cervical ablationperformed using the catheter of FIG. 7M;

FIG. 8 illustrates sinus ablation being performed in a nasal passage byusing the ablation device, in accordance with an embodiment of thepresent specification;

FIG. 9A illustrates bronchial and bullous ablation being performed in apulmonary system by using the ablation device, in accordance with anembodiment of the present specification;

FIG. 9B illustrates bronchial ablation being performed by an ablationdevice having an inflatable balloon with at least one thermallyconducting element attached thereto, in accordance with one embodimentof the present specification;

FIG. 10A illustrates prostate ablation being performed on an enlargedprostrate in a male urinary system by using the device, in accordancewith an embodiment of the present specification;

FIG. 10B is an illustration of transurethral prostate ablation beingperformed on an enlarged prostrate in a male urinary system using anablation device, in accordance with one embodiment of the presentspecification;

FIG. 10C is an illustration of transurethral prostate ablation beingperformed on an enlarged prostrate in a male urinary system using anablation device, in accordance with another embodiment of the presentspecification;

FIG. 10D is a flow chart listing the steps involved in a transurethralenlarged prostate ablation process using an ablation catheter, inaccordance with one embodiment of the present specification;

FIG. 10E is an illustration of transrectal prostate ablation beingperformed on an enlarged prostrate in a male urinary system using anablation device, in accordance with one embodiment of the presentspecification;

FIG. 10F is an illustration of transrectal prostate ablation beingperformed on an enlarged prostrate in a male urinary system using acoaxial ablation device having a positioning element, in accordance withanother embodiment of the present specification;

FIG. 10G is a close-up illustration of the distal end of the catheterand needle tip of the ablation device of FIGS. 10E and 10F;

FIG. 10H is a flow chart listing the steps involved in a transrectalenlarged prostate ablation process using an ablation catheter, inaccordance with one embodiment of the present specification;

FIG. 10I is an illustration of an ablation catheter for permanentimplantation in the body to deliver repeat ablation, in accordance withone embodiment of the present specification;

FIG. 10J is an illustration of a trocar used to place the ablationcatheter of FIG. 10I in the body, in accordance with one embodiment ofthe present specification;

FIG. 10K is an illustration of the catheter of FIG. 10I and the trocarof FIG. 10J assembled for placement of the catheter into tissue targetedfor ablation in the human body, in accordance with one embodiment of thepresent specification;

FIG. 10L is an illustration of pancreatic ablation being performed on apancreatic tumor in accordance with one embodiment of the presentspecification;

FIG. 10M is a flowchart listing the steps involved in one embodiment ofa method of pancreatic ablation;

FIG. 10N is an International Prostate Symptom Score (IPSS)Questionnaire;

FIG. 10O is a Benign Prostatic Hypertrophy Impact Index Questionnaire(BPHIIQ);

FIG. 11 illustrates fibroid ablation being performed in a female uterusby using the ablation device, in accordance with an embodiment of thepresent specification;

FIG. 12A illustrates a blood vessel ablation being performed by anablation device, in accordance with one embodiment of the presentspecification;

FIG. 12B illustrates a blood vessel ablation being performed by anablation device, in accordance with another embodiment of the presentspecification;

FIG. 12C is a flow chart listing the steps involved in a blood vesselablation process using an ablation catheter, in accordance with oneembodiment of the present specification;

FIG. 12D illustrates a cardiac ablation catheter in accordance with oneembodiment of the present specification;

FIG. 12E illustrates cardiac ablation being performed by the cardiacablation catheter of FIG. 12D;

FIG. 12F is a flowchart illustrating the steps involved in oneembodiment of a method of using the catheter of FIG. 12D to ablatecardiac tissue;

FIG. 12G illustrates a cardiac ablation catheter in accordance withanother embodiment of the present specification;

FIG. 12H illustrates the mapping balloon with mapping electrodes of thecatheter of FIG. 12G;

FIG. 12I illustrates a cross sectional view of a mid-shaft portion ofthe catheter of FIG. 12G;

FIG. 12J illustrates a cross sectional view of a distal tip portion ofthe catheter of FIG. 12G;

FIG. 12K is a flowchart illustrating the steps involved in oneembodiment of a method of using the catheter of FIG. 12G to ablatecardiac tissue;

FIG. 13A illustrates a cyst ablation being performed by an ablationdevice, in accordance with one embodiment of the present specification;

FIG. 13B illustrates an ablation device for cyst ablation or solid tumorablation, in accordance with one embodiment of the presentspecification;

FIG. 13C illustrates the distal end of the catheter of the ablationdevice of FIG. 13B;

FIG. 13D illustrates a needle extending from the distal end of thecatheter of the ablation device of FIG. 13B;

FIG. 13E is a close-up illustration of the needle of the ablation deviceof FIG. 13B;

FIG. 13F is a flow chart listing the steps involved in a cyst ablationprocess using an ablation catheter, in accordance with one embodiment ofthe present specification;

FIG. 14 is a flow chart listing the steps involved in a tumor ablationprocess using an ablation catheter, in accordance with one embodiment ofthe present specification;

FIG. 15A illustrates a first view of a non-endoscopic device used forinternal hemorrhoid ablation, in accordance with one embodiment of thepresent specification;

FIG. 15B illustrates a second view of the non-endoscopic device used forinternal hemorrhoid ablation of FIG. 15A, in accordance with oneembodiment of the present specification;

FIG. 15C illustrates a third view of the non-endoscopic device used forinternal hemorrhoid ablation of FIG. 15A, in accordance with oneembodiment of the present specification;

FIG. 15D is a flow chart listing the steps involved in an internalhemorrhoid ablation process using an ablation device, in accordance withone embodiment of the present specification;

FIG. 15E illustrates a non-endoscopic device used for internalhemorrhoid ablation, in accordance with another embodiment of thepresent specification;

FIG. 15F is a flowchart listing the steps of a method for ablating aninternal hemorrhoid using the device of FIG. 15E, in accordance with oneembodiment of the present specification;

FIG. 15G illustrates a non-endoscopic device used for internalhemorrhoid ablation, in accordance with yet another embodiment of thepresent specification;

FIG. 15H is a flowchart listing the steps of a method for ablating aninternal hemorrhoid using the device of FIG. 15G, in accordance with oneembodiment of the present specification;

FIG. 16A illustrates an endoscopic device used for internal hemorrhoidablation, in accordance with one embodiment of the presentspecification;

FIG. 16B is a flow chart listing the steps involved in an internalhemorrhoid ablation process using an endoscopic ablation device, inaccordance with one embodiment of the present specification;

FIG. 17A illustrates a stent used to provide localized ablation to atarget tissue, in accordance with one embodiment of the presentspecification;

FIG. 17B illustrates a catheter used to deploy, and provide an ablativeagent to, the stent of FIG. 17A;

FIG. 17C illustrates the stent of FIG. 17A working in conjunction withthe catheter of FIG. 17B;

FIG. 17D illustrates the stent of FIG. 17A and the catheter of FIG. 17Bpositioned in a bile duct obstructed by a pancreatic tumor;

FIG. 17E is a flow chart listing the steps involved in a hollow tissueor organ ablation process using an ablation stent and catheter, inaccordance with one embodiment of the present specification;

FIG. 18 illustrates a vapor delivery system using an RF heater forsupplying vapor to the ablation device, in accordance with an embodimentof the present specification;

FIG. 19 illustrates a vapor delivery system using a resistive heater forsupplying vapor to the ablation device, in accordance with an embodimentof the present specification;

FIG. 20 illustrates a vapor delivery system using a heating coil forsupplying vapor to the ablation device, in accordance with an embodimentof the present specification;

FIG. 21 illustrates the heating component and coiled tubing of theheating coil vapor delivery system of FIG. 20, in accordance with anembodiment of the present specification;

FIG. 22A illustrates the unassembled interface connection between theablation device and the single use cord of the heating coil vapordelivery system of FIG. 20, in accordance with an embodiment of thepresent specification;

FIG. 22B illustrates the assembled interface connection between theablation device and the single use cord of the heating coil vapordelivery system of FIG. 20, in accordance with an embodiment of thepresent specification;

FIG. 23 illustrates a vapor ablation system using a heater or heatexchange unit for supplying vapor to the ablation device, in accordancewith another embodiment of the present specification;

FIG. 24 illustrates the fluid container, filter member, and pump of thevapor ablation system of FIG. 23;

FIG. 25 illustrates a first view of the fluid container, filter member,pump, heater or heat exchange unit, and microcontroller of the vaporablation system of FIG. 23;

FIG. 26 illustrates a second view of the fluid container, filter member,pump, heater or heat exchange unit, and microcontroller of the vaporablation system of FIG. 23;

FIG. 27 illustrates the unassembled filter member of the vapor ablationsystem of FIG. 23, depicting the filter positioned within;

FIG. 28 illustrates one embodiment of the microcontroller of the vaporablation system of FIG. 23;

FIG. 29 illustrates one embodiment of a catheter assembly for use withthe vapor ablation system of FIG. 23;

FIG. 30 illustrates one embodiment of a heat exchange unit for use withthe vapor ablation system of FIG. 23;

FIG. 31A illustrates another embodiment of a heat exchange unit for usewith the vapor ablation system of the present specification;

FIG. 31B illustrates another embodiment of a heat exchange unit for usewith the vapor ablation system of the present specification;

FIG. 31C illustrates a heat exchange unit and catheter with a syringepump operationally coupled to a fluid filled syringe, in accordance withone embodiment of the present specification;

FIG. 32A illustrates the use of induction heating to heat a chamber;

FIG. 32B is a flow chart listing the steps involved in using inductionheating to heat a chamber;

FIG. 33A illustrates one embodiment of a coil used with inductionheating in the vapor ablation system of the present specification;

FIG. 33B illustrates one embodiment of a catheter handle used withinduction heating in the vapor ablation system of the presentspecification;

FIG. 33C illustrates a disassembled coil component and heating chamberof an induction heating system in accordance with one embodiment of thepresent specification;

FIG. 33D illustrates an assembled induction heating system comprisingthe coil component and heating chamber of FIG. 33C;

FIG. 33E illustrates a first conventional endoscope handle for use withan induction heating system of the present specification;

FIG. 33F illustrates a second conventional endoscope handle for use withan induction heating system of the present specification;

FIG. 33G illustrates a dissembled coil component and heating chamber ofan induction heating system for use with an endoscope, in accordancewith one embodiment of the present specification;

FIG. 33H illustrates an assembled induction heating system for use withan endoscope comprising the coil component and heating chamber of FIG.33G;

FIG. 33I illustrates a dissembled coil component and heating chamber ofan induction heating system for use with an endoscope, in accordancewith another embodiment of the present specification;

FIG. 33J illustrates an assembled induction heating system for use withan endoscope comprising the coil component and heating chamber of FIG.33I;

FIG. 33K illustrates an induction heating system comprising a handleconfigured to be attached to a conventional endoscope handle, inaccordance with one embodiment of the present specification;

FIG. 33L is a cross-sectional illustration of an induction heatingsystem comprising a handle and having a wheel mechanism for moving acoil component relative to a heating chamber, in accordance with oneembodiment of the present specification;

FIG. 33M illustrates an induction heating system comprising a heatingchamber in a first position relative to a coil component, in accordancewith one embodiment of the present specification;

FIG. 33N illustrates the induction heating system of FIG. 33M with theheating chamber in a second position relative to the coil component;

FIG. 33O illustrates an induction heating system comprising a firsthandle component in a first position relative to a second handlecomponent, in accordance with one embodiment of the presentspecification;

FIG. 33P illustrates the induction heating system of FIG. 33O with thefirst handle component in a second position relative to the secondhandle component;

FIG. 33Q illustrates a luer lock mechanism at a distal end of a handleof an induction heating system, in accordance with one embodiment of thepresent specification;

FIG. 33R illustrates a spring loaded connector in a first position at adistal end of a handle of an induction heating system, in accordancewith one embodiment of the present specification;

FIG. 33S illustrates the spring loaded connector of FIG. 33R in a secondposition;

FIG. 33T illustrates a closed loop vapor delivery system for use with anendoscope, in accordance with one embodiment of the presentspecification;

FIG. 33U is a flowchart illustrating the steps involved in oneembodiment of a method of providing vapor ablation therapy using thevapor delivery system of FIG. 33T;

FIG. 33V illustrates a closed loop vapor delivery system for use with anendoscope, in accordance with another embodiment of the presentspecification;

FIG. 33W is a flowchart illustrating the steps involved in oneembodiment of a method of providing vapor ablation therapy using thevapor delivery system of FIG. 33V;

FIG. 33X illustrates a closed loop vapor delivery system for use with anendoscope, in accordance with yet another embodiment of the presentspecification;

FIG. 33Y is a flowchart illustrating the steps involved in oneembodiment of a method of providing vapor ablation therapy using thevapor delivery system of FIG. 33X;

FIG. 34A is a front view cross sectional diagram illustrating oneembodiment of a catheter used with induction heating in the vaporablation system of the present specification;

FIG. 34B is a longitudinal view cross sectional diagram illustrating oneembodiment of a catheter used with induction heating in the vaporablation system of the present specification;

FIG. 34C is a longitudinal view cross sectional diagram illustratinganother embodiment of a catheter with a metal spiral used with inductionheating in the vapor ablation system of the present specification;

FIG. 34D is a longitudinal view cross sectional diagram illustratinganother embodiment of a catheter with a mesh used with induction heatingin the vapor ablation system of the present specification;

FIG. 35 illustrates one embodiment of a heating unit using microwaves toconvert fluid to vapor in the vapor ablation system of the presentspecification;

FIG. 36A illustrates a catheter assembly having an inline chamber forheat transfer in accordance with one embodiment of the presentspecification;

FIG. 36B illustrates the catheter assembly of FIG. 36A including anoptional handle;

FIG. 36C illustrates the catheter assembly of FIG. 36B connected to agenerator having a heating element and a pump, in accordance with oneembodiment of the present specification;

FIG. 36D illustrates a catheter assembly having an inline chamber forheat transfer in accordance with another embodiment of the presentspecification;

FIG. 36E illustrates a catheter assembly connected to a heating chamberin accordance with one embodiment of the present specification;

FIG. 37A illustrates a heating chamber packed with metal tubes inaccordance with one embodiment of the present specification;

FIG. 37B illustrates a heating chamber packed with metal beads inaccordance with one embodiment of the present specification;

FIG. 37C illustrates a heating chamber packed with metal filings inaccordance with one embodiment of the present specification;

FIG. 37D is a graph illustrating Curie temperature (T_(c)) as a functionof nickel content as described in Special-Purpose Nickel Alloys, ASMSpecialty Handbook: Nickel, Cobalt, and Their Alloys, Dietrich, et al.,ASM International, 2000, p 92-105, FIG. 4;

FIG. 37E is an illustration of one embodiment of a vapor ablation systemwith a Curie point induction heating chamber;

FIG. 37F is an illustration of another embodiment of a vapor ablationsystem with a Curie point material induction heating chamber including auser interface;

FIG. 37G is a flowchart illustrating the steps involved in oneembodiment of a method of generating steam using a vapor ablation systemhaving a Curie point material heating chamber;

FIG. 37H is a flow chart illustrating the steps involved in tissueablation using various ablation systems of the present specification;

FIG. 38A illustrates a cross-sectional view of one embodiment of acatheter having an internal groove to decrease flow resistance;

FIG. 38B illustrates an on-end view of one embodiment of a catheterhaving an internal groove to decrease flow resistance;

FIG. 39A illustrates a cross-sectional view of a double layered catheterin accordance with one embodiment of the present specification;

FIG. 39B illustrates a cross-sectional view of a double layered catheterin accordance with another embodiment of the present specification;

FIG. 39C illustrates a cross-sectional view of a double layered catheterin accordance with another embodiment of the present specification

FIG. 39D illustrates a catheter having the double layer configurationdepicted in FIG. 39B;

FIG. 40A is an illustration of a vapor ablation system using inductionheating in accordance with one embodiment of the present specification;

FIG. 40B is a graph illustrating the behavior, in relation to the idealgas law, of a plurality of gases as they are heated to hightemperatures;

FIG. 40C is an illustration of one embodiment of a catheter for use withthe vapor ablation systems of the present specification;

FIG. 40D is a flowchart listing the steps of a method of using theablation catheter of FIG. 40C, in accordance with one embodiment of thepresent specification;

FIG. 40E is a flowchart listing the steps of a method of using theablation catheter of FIG. 40C, in accordance with another embodiment ofthe present specification;

FIG. 40F is an illustration of one embodiment of a positioning elementof an ablation catheter, depicting a plurality of thermally conductingelements attached thereto;

FIG. 40G is an illustration of one embodiment of a positioning elementof an ablation catheter, depicting a plurality of hollow thermallyconducting elements attached thereto;

FIG. 40H is an illustration of an ablation catheter having a pluralityof thermally conducting elements within a positioning element, inaccordance with one embodiment of the present specification;

FIG. 40I is an illustration of an ablation catheter having a thermallyconducting element attached to an outer surface of a positioningelement;

FIG. 40J is a flowchart listing the steps of a method of using a vaporablation system in accordance with one embodiment of the presentspecification;

FIG. 40K is a flowchart listing the steps of a method of using a vaporablation system in accordance with another embodiment of the presentspecification;

FIG. 41A is an illustration of the components of a vapor ablation systemin accordance with one embodiment of the present specification;

FIG. 41B is an illustration of the vapor ablation system of FIG. 41Awith the heating chamber cover removed;

FIG. 41C is a close-up illustration of the uncovered heating chamber ofthe vapor ablation system of FIG. 41B;

FIG. 41D is an illustration of the vapor ablation system of FIG. 41Awith the covers removed from the system components;

FIG. 41E is a close-up illustration of the dosing pump and heavy-gaugesteel enclosure of the vapor ablation system of FIG. 41A;

FIG. 41F is a close-up illustration of the dosing pump, with intake portand discharge ports, of the vapor ablation system of FIG. 41A;

FIG. 41G is a close-up illustration of the main electronics board withancillary electronics within the heavy-gauge steel enclosure of thevapor ablation system of FIG. 41A;

FIG. 41H is a block diagram of the induction heater drive electronics inaccordance with one embodiment of the present specification;

FIG. 41I is a graph illustrating waveforms generated by the inductionheater drive electronics depicted in FIG. 41H;

FIG. 41J is an illustration of a triac phase control circuit of theinduction heater drive electronics depicted in FIG. 41H;

FIG. 42 is an illustration of eddy currents induced by an alternatingelectromagnetic field;

FIG. 43 is a graph illustrating the variation in magnetic hysteresisbetween different ferromagnetic materials;

FIG. 44 is an illustration depicting a variety metal rods and a coveringtube for an induction heating chamber in accordance with someembodiments of the present specification;

FIG. 45 is an illustration of a metal rod having a threaded outersurface and a tube having a threaded inner surface for a heating chamberin accordance with one embodiment of the present specification;

FIG. 46A is an illustration of a smooth metal rod and a tube of aheating chamber in accordance with one embodiment of the presentspecification;

FIG. 46B is a top-down illustration of the metal rod positioned withinthe tube of the heating chamber of FIG. 46A;

FIG. 46C is a flow chart illustrating the steps involved in generatingsteam using an induction heated metal core, in accordance with oneembodiment of the present specification;

FIG. 47 is an illustration of a distal end of a metal rod of a heatingchamber with a thermocouple positioned therein;

FIG. 48A is an illustration of a tube of a heating chamber and athermocouple sheath in accordance with one embodiment of the presentspecification;

FIG. 48B is an illustration of the tube of FIG. 48A with thethermocouple sheath positioned within the cutout;

FIG. 48C is an illustration of the tube and thermocouple sheath of FIG.48B with first and second flanges positioned over said tube and sheathin accordance with one embodiment of the present specification;

FIG. 48D is an illustration of the tube, sheath, and flanges of FIG. 48Cwith a thermal compound applied to the components in accordance with oneembodiment of the present specification;

FIG. 48E is an illustration of the tube, sheath, flanges, and thermalcompound of FIG. 48D with an induction coil wrapped about said tube andsheath;

FIG. 49A is an illustration of the distal end of a heating chamberdepicting a lead of a thermocouple positioned within the metal core ofthe chamber in accordance with one embodiment of the presentspecification;

FIG. 49B is an illustration of a manifold configured to route the leadsof a heating core thermocouple in accordance with one embodiment of thepresent specification;

FIG. 49C is an illustration of the manifold of FIG. 49B with acompression screw positioned in the left section;

FIG. 49D is a top-down illustration of the manifold of FIG. 49Cdepicting the routes taken by the thermocouple leads within the manifoldas they exit the fluid pathway;

FIG. 49E is an illustration of the manifold of FIG. 49D with a luer lockconnector attached to the distal end of the manifold;

FIG. 49F is an illustration of the manifold of FIG. 49E depicting theluer lock connector and adapter wrapped in a thermally insulatingmaterial;

FIG. 49G is a schematic diagram of a thermocouple analog front end inaccordance with one embodiment of the present specification;

FIG. 49H is a flowchart listing the steps involved in regulating steamtemperature and vapor ablation system stability, in accordance with oneembodiment of the present specification;

FIG. 49I is a block diagram illustrating a vapor ablation kit comprisinga handheld induction heating mechanism in accordance with one embodimentof the present specification;

FIG. 49J is an illustration of a vapor ablation kit comprising a waterreservoir, heating chamber, and catheter, in accordance with anotherembodiment of the present specification;

FIG. 49K is a vertical cross section illustration of an inductionheating chamber in accordance with one embodiment of the presentspecification;

FIG. 49L is an illustration of the induction heating chamber of FIG. 49Kdepicting the various components of the chamber in further detail;

FIG. 49M is a horizontal cross section illustration of the inductionheating chamber of FIG. 49K;

FIG. 49N is an illustration of a vapor delivery system including atleast one sensor for use with an endoscope, in accordance with oneembodiment of the present specification;

FIG. 49O is a flowchart illustrating the steps involved in oneembodiment of a method of delivering vapor ablation therapy using acatheter with a coil in the generator;

FIG. 49P is a flowchart illustrating the steps involved in oneembodiment of a method of delivering vapor ablation therapy using acatheter with a coil in the handle;

FIG. 49Q is a flowchart illustrating the steps involved in oneembodiment of a method of using inflatable balloons of a vapor ablationcatheter to determine ablation dose;

FIG. 50 is a screenshot of a graphical user interface (GUI) home screenin accordance with one embodiment of the present specification;

FIG. 51 is a screenshot of a graphical user interface (GUI) systemstatus screen in accordance with one embodiment of the presentspecification;

FIG. 52 is a screenshot of a graphical user interface (GUI) flow, heat,temps screen in accordance with one embodiment of the presentspecification;

FIG. 53 is a screenshot of a graphical user interface (GUI) heat,pressure screen in accordance with one embodiment of the presentspecification;

FIG. 54 is a screenshot of a graphical user interface (GUI) program Rxscreen in accordance with one embodiment of the present specification;and

FIG. 55 is a screenshot of a graphical user interface (GUI) deliver Rxscreen in accordance with one embodiment of the present specification.

DETAILED DESCRIPTION

The present specification is directed toward an ablation devicecomprising a catheter with one or more centering or positioningattachments at one or more ends of the catheter to affix the catheterand its infusion port at a fixed distance from the ablative tissue whichis not affected by the movements of the organ. The arrangement of one ormore spray ports allows for uniform spray of the ablative agentproducing a uniform ablation of a large area, such as encountered inBarrett's esophagus or for endometrial ablation. The flow of ablativeagent is controlled by the microprocessor and depends upon one or moreof the length or area of tissue to be ablated, type and depth of tissueto be ablated, and distance of the infusion port from or in the tissueto be ablated.

The present specification is also directed toward a disposable steamgeneration system which enables the real-time, on demand generation ofmicro-dose amounts of steam. The disposable portion comprises a watersource, such as a syringe or bag, in fluid communication with a heatingchamber which is in fluid communication with a catheter. The disposable,single-use water source—heating chamber—catheter series of connectedcomponents is designed to reliably deliver steam without worrying aboutthe sterility of the water, contamination arising from multiple uses,the cost and/or logistics of cleaning, or the risk of leakage of vaporcausing injury to the operator.

The present specification is also directed toward a device to be used inconjunction with a tissue ablation system, comprising: a handle with apressure-resistant port on its distal end, a flow channel through whichan ablative agent can travel, and one or more connection ports on itsproximal end for the inlet of said ablative agent and for an RF feed oran electrical feed; an insulated catheter that attaches to saidpressure-resistant port of said handle, containing a shaft through whichan ablative agent can travel and one or more ports along its length forthe release of said ablative agent; and, one or more positioningelements attached to said catheter shaft at one or more separatepositions, wherein said positioning element(s) is configured to positionsaid catheter at a predefined distance from or in the tissue to beablated.

In one embodiment, the handle has one pressure-resistant port for theattachment of both an ablative agent inlet and an RF feed. In anotherembodiment, the handle has one separate pressure-resistant port for theattachment of an ablative agent inlet and one separate port for theattachment of an RF feed or an electrical feed.

The present specification is also directed toward a device to be used inconjunction with a tissue ablation system, comprising: a handle with apressure-resistant port on its distal end, a flow channel passingthrough said handle which is continuous with a pre-attached cord throughwhich an ablative agent can travel, and a connection port on itsproximal end for an RF feed or an electrical feed; an insulated catheterthat attaches to said pressure-resistant port of said handle, containinga shaft through which an ablative agent can travel and one or more portsalong its length for the release of said ablative agent; and, one ormore positioning elements attached to said catheter shaft at one or moreseparate positions, wherein said positioning element(s) is configured toposition said catheter at a predefined distance from or in the tissue tobe ablated. In one embodiment, the distal end of said catheter isdesigned to puncture the target tissue to deliver ablative agent to thecorrect depth and location.

The present specification is also directed toward a device to be used inconjunction with a tissue ablation system, comprising: an esophagealprobe with a pressure-resistant port on its distal end, a flow channelthrough which an ablative agent can travel, and one or more connectionports on its proximal end for the inlet of said ablative agent and foran RF feed; an insulated catheter that attaches to saidpressure-resistant port of said esophageal probe, containing a shaftthrough which an ablative agent can travel and one or more ports alongits length for the release of said ablative agent; and, one or moreinflatable positioning balloons at either end of said catheterpositioned beyond said one or more ports, wherein said positioningballoons are configured to position said catheter at a predefineddistance from the tissue to be ablated.

In one embodiment, the catheter is dual lumen, wherein a first lumenfacilitates the transfer of ablative agent and a second lumen containsan electrode for RF ablation.

In one embodiment, the catheter has differential insulation along itslength.

In one embodiment, the one or more balloons are filled with air which isin thermal contact with the ablative agent being delivered such that theair expands during the delivery of ablative agent and contracts afterthe cessation of delivery of the ablative agent. This results in a firstvolume of the balloon prior to the initiation of therapy which is usedfor measurement of the dimensions of the hollow organ. The volume of theballoon increases to a second volume during the initiation of therapywhich serves an occlusive function to better control the distribution ofablative energy. In various embodiments, the second volume is greaterthan the first volume.

In one embodiment, the volume of the inner balloon is used to controlthe pressure exerted by the outer balloon on the wall of the holloworgan. The pressure in the inner balloon is monitored and air is addedto or removed from the inner balloon to maintain a desirable therapeuticpressure in the outer balloon.

The present specification is also directed toward a vapor deliverysystem used for supplying vapor to an ablation device, comprising: aliquid reservoir, wherein said reservoir includes a pressure-resistantoutlet connector for the attachment of a reusable cord; a reusable cordconnecting the outlet of said reservoir to the inlet of a heatingcomponent; a powered heating component containing a length of coiledtubing within for the conversion of liquid to vapor andpressure-resistant connections on both the inlet and outlet ends of saidheating component; and, a single use cord connecting apressure-resistant inlet port of a vapor based ablation device to theoutlet of said heating component.

In one embodiment, the liquid reservoir is integrated within anoperating room equipment generator.

In one embodiment, the liquid is water and resultant said vapor issteam.

In one embodiment, the pressure-resistant connections are of a luer locktype.

In one embodiment, the coiled tubing is copper.

In one embodiment, the vapor delivery system used for supplying vapor toan ablation device further comprises a foot pedal used by the operatorto deliver more vapor to the ablation device.

The present specification is also directed toward a device and a methodfor ablating a hollow tissue or organ by replacing the natural contentsof the tissue or organ with a conductive medium and then delivering anablative agent to the conductive medium to ablate the tissue or organ.

The present specification is also directed toward a device and methodfor ablating a blood vessel consisting of replacing the blood in thetargeted vessel with a conductive medium and then delivering an ablativeagent to the conductive medium to ablate the vessel. In one embodiment,the device and method further comprise a means or step for stopping theflood of blood into the target vessel. In one embodiment, blood flow isoccluded by the application of a tourniquet proximal to the targetvessel. In another embodiment, blood flow is occluded by the applicationof at least one intraluminal occlusive element. In one embodiment, theat least one intraluminal occlusive element includes at least oneunidirectional valve. In one embodiment, the intraluminal occlusiveelement is used to position the source or port delivering the ablativeagent in the vessel.

The present specification is also directed toward a device and a methodfor ablating a cyst by inserting a catheter into the cyst, replacing aportion of the contents of the cyst with a conductive medium, adding anablative agent to the conductive medium, and conducting ablative energyto the cyst wall through the medium to ablate the cyst.

The present specification is also directed toward a device and a methodfor ablating a tumor by inserting a catheter into the tumor, replacing aportion of the contents of the tumor with a conductive medium, adding anablative agent to the conductive medium, and conducting ablative energyto the tumor wall through the medium to ablate the tumor.

The present specification is also directed toward a device and methodfor ablating a structure in or proximate the wall of a hollow organ byinserting a catheter with a thermally insulating balloon at a distal endinto the hollow organ and proximate the structure to be ablated,inflating the balloon to a pre-determined volume with air such that asurface of the balloon becomes positioned proximate said wall, anddelivering thermal energy through a thermally conducting member in theballoon and into said structure. The balloon includes a thermallyconductive member for the conduction of thermal energy from inside ofthe balloon to the wall of the hollow organ. The passage of thermalenergy into the balloon heats the air in the balloon, further expandingthe balloon and forcing the thermally conducting member into the wall ofthe hollow organ and simultaneously delivering thermal energy to saidwall. In various embodiments, the thermally conductive member comprisesa solid or hollow needle. In various embodiments, the thermallyconductive member further comprises a valve which is regulated bytemperature, pressure or both.

In various embodiments, any one of the devices described above comprisesa catheter and includes at least one port for delivering the conductivemedium and at least one separate port for delivering the ablative agent.In another embodiment, the device comprises a catheter and includes atleast one port for delivering both the conductive medium and theablative agent. Optionally, in one embodiment, the device furtherincludes at least one port for removing the contents of the hollow organor tissue or for removing the conductive medium. In various embodiments,the at least one port for removing contents or conductive medium is thesame port for delivering the conductive medium and/or ablative agent oris a separate port. In one embodiment, the ablative agent is a thermalagent, such as steam. In another embodiment, the ablative agent is acryogen, such as liquid nitrogen.

Optionally, in one embodiment, sensors are included in the device tomeasure and control the flow of the ablative agent. In one embodiment,conductive medium is water. In another embodiment, the conductive mediumis saline.

In various embodiments, any one of the devices described above comprisesa coaxial catheter having an outer, insulating sheath and an innertubular member for delivery of the conductive medium and the ablativeagent. In various embodiments, the inner tubular member is thermallyinsulating.

Optionally, in various embodiments, any one of the devices describedabove includes echogenic elements to assist with the placement of thedevice into the target tissue under ultrasonic guidance. Optionally, invarious embodiments, any one of the devices described above includesradio-opaque elements to assist with the placement of the device intothe target tissue under radiologic guidance.

The present specification is also directed toward a system and method ofinternal hemorrhoid ablation by inserting a hollow, tubular device intoa patient's rectum, applying suction to the device to draw the targethemorrhoid tissue into a slot in the device, and delivering an ablativeagent, such as steam, through a port in the device to ablate thehemorrhoid. In one embodiment, the system includes a device composed ofa thermally insulated material to avoid transfer of vapor heat tosurrounding rectal mucosa. In another embodiment, the system has amechanism for puncturing the mucosa to deliver the ablative agentdirectly into the submucosa closer to the hemorrhoid. In anotherembodiment, the system has a mechanism for cooling the mucosa so as toreduce the ablative damage to the mucosa.

The present specification is also directed toward a system and method ofinternal hemorrhoid ablation by inserting a hollow, tubular device intoa patient's rectum, applying suction to the device to draw the targethemorrhoid tissue into a slot in the device, inserting a needle throughthe slot and into the rectal submucosa or the wall of the hemorrhoidvessel, and delivering an ablative agent through the needle to ablatethe hemorrhoid.

The present specification is also directed toward a system and method ofinternal hemorrhoid ablation by inserting a device into a patient's analcanal, thus opening said anal canal, identifying the abnormal hemorrhoidtissue, engaging said hemorrhoid tissue with the device, compressingsaid hemorrhoid tissue to reduce its cross-sectional area, anddelivering ablative energy to the hemorrhoid tissue to ablate thehemorrhoid.

The present specification is also directed toward a device and methodfor endometrial treatment by inserting a coaxial catheter comprising aninternal catheter and an external catheter into the cervix, wherein theexternal catheter engages the cervix and the internal catheter extendsinto the uterus. The internal catheter continues until it reaches thefundus of the uterus, at which point the depth of insertion of theinternal catheter is used to measure the depth of the uterine cavity. Anablative agent, such as steam, is then delivered via the at least oneport on the internal catheter to provide treatment to the endometrium.Optionally, in various embodiments, the catheter includes pressuresensors and/or temperature sensors to measure the intrauterine pressureor temperature. Optionally, in one embodiment, the external catheterfurther comprises a plurality of fins which engage the cervix andprevent the escape of ablative agent. In one embodiment, the fins arecomposed of silicon. Optionally in one embodiment, the coaxial catheterfurther includes a locking mechanism between the external catheter andinternal catheter that, when engaged, prevents the escape of ablativeagent. In one embodiment, the locking mechanism is of a luer lock type.Optionally, the flow of ablative agent is controlled by the number ofopen ports which in turn is controlled by the length of the exposedinternal catheter.

The present specification is also directed toward a device and methodfor endometrial ablation using a balloon catheter with a plurality ofcoaxial balloon structures wherein an inner balloon is a compliantballoon structure and an outer balloon is a non-compliant balloonstructure shaped to approximate the uterine cavity shape, size orvolume. The inflation of the inner balloon with air results in expansionof the outer balloon to approximate the endometrial cavity. An ablativeagent is passed through a space between the two balloons. Thermal energyfrom the ablative agent is delivered through the outer balloon into theendometrial cavity. In various embodiments, the outer balloon is porous,allowing the passage of vapor and thermal energy, or non-porous,allowing the passage of thermal energy only. The passage of thermalenergy between the two balloons leads to expansion of the air in theinner balloon, further approximating the outer balloon shape closer tothe endometrium for more efficient thermal energy delivery duringtherapy. The air cools when ablative energy is not being delivered,relieving the pressure on the outer balloon and the endometrial cavityand preventing endometrial perforation from prolonged overexpansion. Inanother embodiment, the outer balloon is partially compliant. In anotherembodiment, the compliance of the two balloons is substantiallyequivalent.

The present specification is also directed toward device and method fortissue ablation comprising a stent covered by a membrane that conductsan ablative agent, such as steam, or ablative energy from inside thestent lumen to the external surface of the stent for ablation ofsurrounding tissue. In one embodiment, the stent has a pre-deploymentshape and a post-deployment shape. The pre-deployment shape isconfigured to assist with placement of the stent. In one embodiment, themembrane is composed of a thermally conductive material. In oneembodiment, the membrane includes a plurality of openings that allow forthe passage of ablative agent or energy from the stent lumen to thetissue surrounding the stent. In one embodiment, the stent is used totreat obstruction in a hollow organ. In one embodiment, the membrane ismade of a thermally conductive material that allows for transfer ofenergy from the inside of the stent to the outside of the stent into thesurrounding tissue.

In one embodiment, a catheter is used to deliver the ablative agent tothe stent. The catheter includes at least one port at its distal end forthe delivery of ablative agent into the lumen of the stent. In oneembodiment, the catheter includes one or more positioning elementsconfigured to fix the catheter at a predefined distance from the stent.The positioning element(s) also acts as an occlusive member to preventthe flow of ablative agent out of the ends of the stent. In oneembodiment, the catheter is composed of a thermally insulating material.Optionally, in various embodiments, the catheter includes additionallumens for the passage of a guidewire or radiologic contrast material.

The present specification is also directed toward a device and methodfor transrectal prostate ablation. An endoscope is inserted into therectum for visualization of the prostate. In one embodiment, theendoscope is an echoendoscope. In another embodiment, the visualizationis achieved via transrectal ultrasound. A catheter with a needle tip ispassed transrectally into the prostate and an ablative agent, such asvapor, is delivered through the needle tip and into the prostatictissue. The prostatic tissue chosen is ideally away from the prostaticurethra to avoid damage to the prostatic urethra. In one embodiment, theneedle tip is an echotip or sonolucent tip that can be detected by theechoendoscope to aid in placement within the prostatic tissue. In oneembodiment, the catheter and needle tip are composed of a thermallyinsulating material. Optionally, in one embodiment, an additionalcatheter is placed in the patient's urethra to insert fluid to cool theprostatic urethra. In one embodiment, the cooling fluid has atemperature of less than 37° C. Optionally, in one embodiment, thecatheter further comprises a positioning element which positions theneedle tip at a predetermined depth in the prostatic tissue. In oneembodiment, the positioning element is a compressible disc.

The present specification is also directed toward an ablation catheterassembly comprising a catheter body, a first inline chamber for heatingan ablative agent, and a second inline chamber for storing said ablativeagent. A pump drives a piston located within the second inline chamberto push a fluid through a one-way valve and into the first inlinechamber. A heating element heats the first inline chamber, convertingthe fluid from a liquid into a vapor. The vapor then travels through thecatheter and is delivered to the target tissue site for ablation. Invarious embodiments, the first chamber is composed of a ferromagnetic orthermally conducting material. In one embodiment, the pump is controlledby a microprocessor to deliver ablative agent at a predetermined rate.In one embodiment, sensors in the catheter provide informationmicroprocessor to control the delivery rate. In one embodiment, thecatheter includes an insulated handle to allow for safe manipulation ofthe catheter assembly by an operator. In various embodiments, theheating element is a resistive heater, RF heater, microwave heater, orelectromagnetic heater.

In various embodiments, the first inline chamber comprises a pluralityof channels within to increase the contact surface area of the ablativeagent with the walls of the chamber to provide for more efficientheating of said agent. In various embodiments, the channels comprisemetal tubes, metal beads, or metal filings. In various embodiments, thechamber has adequate thermal mass to maintain the chamber at a constanttemperature (+/−25% of ideal temperature) during heating of the ablativeagent. In one embodiment, the inner surface of the catheter includes agroove pattern to reduce the resistance to flow of the ablative agentwithin the catheter. In one embodiment, the catheter comprises twowalls, an inner wall and an outer wall, with a thin insulating layer inbetween, to insulate the catheter and prevent thermal trauma to anoperator from the heated ablative agent within said catheter.

In various embodiments, the ablation devices and catheters described inthe present specification are used in conjunction with any one or moreof the heating systems described in U.S. patent application Ser. No.13/486,980, entitled “Method and Apparatus for Tissue Ablation”, filedon Jun. 1, 2012 and assigned to the applicant of the present invention,which is herein incorporated by reference in its entirety.

“Treat,” “treatment,” and variations thereof refer to any reduction inthe extent, frequency, or severity of one or more symptoms or signsassociated with a condition.

“Duration” and variations thereof refer to the time course of aprescribed treatment, from initiation to conclusion, whether thetreatment is concluded because the condition is resolved or thetreatment is suspended for any reason. Over the duration of treatment, aplurality of treatment periods may be prescribed during which one ormore prescribed stimuli are administered to the subject.

“Period” refers to the time over which a “dose” of stimulation isadministered to a subject as part of the prescribed treatment plan.

The term “and/or” means one or all of the listed elements or acombination of any two or more of the listed elements.

The terms “comprises” and variations thereof do not have a limitingmeaning where these terms appear in the description and claims.

Unless otherwise specified, “a,” “an,” “the,” “one or more,” and “atleast one” are used interchangeably and mean one or more than one.

For any method disclosed herein that includes discrete steps, the stepsmay be conducted in any feasible order. And, as appropriate, anycombination of two or more steps may be conducted simultaneously.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, 5, etc.). Unless otherwise indicated, all numbersexpressing quantities of components, molecular weights, and so forthused in the specification and claims are to be understood as beingmodified in all instances by the term “about.” Accordingly, unlessotherwise indicated to the contrary, the numerical parameters set forthin the specification and claims are approximations that may varydepending upon the desired properties sought to be obtained by thepresent specification. At the very least, and not as an attempt to limitthe doctrine of equivalents to the scope of the claims, each numericalparameter should at least be construed in light of the number ofreported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the specification are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. All numerical values, however, inherently contain a rangenecessarily resulting from the standard deviation found in theirrespective testing measurements.

Ablative agents such as steam, heated gas or cryogens, such as, but notlimited to, liquid nitrogen are inexpensive and readily available andare directed via the infusion port onto the tissue, held at a fixed andconsistent distance, targeted for ablation. This allows for uniformdistribution of the ablative agent on the targeted tissue. The flow ofthe ablative agent is controlled by a microprocessor according to apredetermined method based on the characteristic of the tissue to beablated, required depth of ablation, and distance of the port from thetissue. The microprocessor may use temperature, pressure or othersensing data to control the flow of the ablative agent. In addition, oneor more suction ports are provided to suction the ablation agent fromthe vicinity of the targeted tissue. The targeted segment can be treatedby a continuous infusion of the ablative agent or via cycles of infusionand removal of the ablative agent as determined and controlled by themicroprocessor.

It should be appreciated that the devices and embodiments describedherein are implemented in concert with a controller that comprises amicroprocessor executing control instructions. The controller can be inthe form of any computing device, including desktop, laptop, and mobiledevice, and can communicate control signals to the ablation devices inwired or wireless form.

The present invention is directed towards multiple embodiments. Thefollowing disclosure is provided in order to enable a person havingordinary skill in the art to practice the invention. Language used inthis specification should not be interpreted as a general disavowal ofany one specific embodiment or used to limit the claims beyond themeaning of the terms used therein. The general principles defined hereinmay be applied to other embodiments and applications without departingfrom the spirit and scope of the invention. Also, the terminology andphraseology used is for the purpose of describing exemplary embodimentsand should not be considered limiting. Thus, the present invention is tobe accorded the widest scope encompassing numerous alternatives,modifications and equivalents consistent with the principles andfeatures disclosed. For purpose of clarity, details relating totechnical material that is known in the technical fields related to theinvention have not been described in detail so as not to unnecessarilyobscure the present invention.

It should be noted herein that any feature or component described inassociation with a specific embodiment may be used and implemented withany other embodiment unless clearly indicated otherwise.

FIG. 1A illustrates an ablation device, in accordance with an embodimentof the present specification. The ablation device comprises a catheter10 having a distal centering or positioning attachment which is aninflatable balloon 11. The catheter 10 is made of or covered with aninsulated material to prevent the escape of ablative energy from thecatheter body. The ablation device comprises one or more infusion ports12 for the infusion of ablative agent and one or more suction ports 13for the removal of ablative agent. In one embodiment, the infusion port12 and suction port 13 are the same. In one embodiment, the infusionports 12 can direct the ablative agent at different angles. Ablativeagent is stored in a reservoir 14 connected to the catheter 10. Deliveryof the ablative agent is controlled by a microprocessor 15 andinitiation of the treatment is controlled by a treating physician usingan input device, such as a foot-paddle 16. In other embodiments, theinput device could be a voice recognition system (that is responsive tocommands such as “start”, “more”, “less”, etc.), a mouse, a switch,footpad, or any other input device known to persons of ordinary skill inthe art. In one embodiment, microprocessor 15 translates signals fromthe input device, such as pressure being placed on the foot-paddle orvocal commands to provide “more” or “less” ablative agent, into controlsignals that determine whether more or less ablative agent is dispensed.Optional sensor 17 monitors changes in an ablative tissue or itsvicinity to guide flow of ablative agent. In one embodiment, optionalsensor 17 also includes a temperature sensor. Optional infrared,electromagnetic, acoustic or radiofrequency energy emitters and sensors18 measure the dimensions of the hollow organ.

In one embodiment, a user interface included with the microprocessor 15allows a physician to define device, organ, and condition which in turncreates default settings for temperature, cycling, volume (sounds), andstandard RF settings. In one embodiment, these defaults can be furthermodified by the physician. The user interface also includes standarddisplays of all key variables, along with warnings if values exceed orgo below certain levels.

The ablation device also includes safety mechanisms to prevent usersfrom being burned while manipulating the catheter, including insulation,and optionally, cool air flush, cool water flush, and alarms/tones toindicate start and stop of treatment.

In one embodiment, the inflatable balloon has a diameter of between 1 mmand 10 cm. In one embodiment, the inflatable balloon is separated fromthe ports by a distance of 1 mm to 10 cm. In one embodiment, the size ofthe port openings is between 1 μm and 1 cm. It should be appreciatedthat the inflatable balloon is used to fix the device and therefore isconfigured to not contact the ablated area. The inflatable balloon canbe any shape that contacts the hollow organ at 3 or more points. One ofordinary skill in the art will recognize that, using triangulation, onecan calculate the distance of the catheter from the lesion.Alternatively, the infrared, electromagnetic, acoustic or radiofrequencyenergy emitters and sensors 18 can measure the dimensions of the holloworgan. The infrared, electromagnetic, acoustic or radiofrequency energyis emitted from the emitter 18 and is reflected back from the tissue tothe detector in the emitter 18. The reflected data can be used todetermine the dimension of the hollow cavity. It should be appreciatedthat the emitter and sensor 18 can be incorporated into a singletransceiver that is capable of both emitting energy and detecting thereflected energy.

FIG. 1B illustrates another embodiment of a catheter 110 for use withthe ablation device of FIG. 1A. The catheter 110 includes an inlet port119 and an insufflation port 120 at its proximal end. An ablative agentis introduced into the catheter 110 via the inlet port 119 and isdelivered to a target region by at least one delivery port 112 at thedistal end of the catheter 110. Air is introduced at the insufflationport 120 to inflate at least one positioning element 111 at the distalend of the catheter. In one embodiment, the at least one positioningelement 111 is a balloon.

FIG. 2A illustrates a longitudinal section of the ablation device,depicting a distribution of infusion ports. FIG. 2B illustrates a crosssection of a distribution of infusion ports on the ablation device, inaccordance with an embodiment of the present specification. Thelongitudinal and cross sectional view of the catheter 10 as illustratedin FIGS. 2A and 2B respectively, show one arrangement of the infusionports 12 to produce a uniform distribution of ablative agent 21 in orderto provide a circumferential area of ablation in a hollow organ 20. FIG.2C illustrates a cross section of a distribution of infusion ports onthe ablation device, in accordance with another embodiment of thepresent specification. The arrangement of the infusion ports 12 asillustrated in FIG. 2C produce a focal distribution of ablative agent 21and a focal area of ablation in a hollow organ 20.

For all embodiments described herein, it should be appreciated that thesize of the port, number of ports, and distance between the ports willbe determined by the volume of ablative agent needed, pressure that thehollow organ can withstand, size of the hollow organ as measured by thedistance of the surface from the port, length of the tissue to beablated (which is roughly the surface area to be ablated),characteristics of the tissue to be ablated and depth of ablationneeded. In one embodiment, there is at least one port opening that has adiameter between 1 μm and 1 cm. In another embodiment, there are two ormore port openings that have a diameter between 1 μm and 1 cm and thatare equally spaced around the perimeter of the device. In someembodiments, the ports optionally have valves for the control of releaseof the ablative agent. In various embodiments, the valves are regulatedeither by pressure, temperature, or both.

FIG. 2D illustrates another embodiment of the ablation device. The vaporablation catheter comprises an insulated catheter 21 with one or morepositioning attachments 22 of known length 23. The vapor ablationcatheter has one or more vapor infusion ports 25. The length 24 of thevapor ablation catheter 21 with infusion ports 25 is determined by thelength or area of the tissue to be ablated. Vapor 29 is deliveredthrough the vapor infusion ports 25. The catheter 21 is preferablypositioned in the center of the positioning attachment 22, and theinfusion ports 25 are arranged circumferentially for circumferentialablation and delivery of vapor. In another embodiment, the catheter 21can be positioned toward the periphery of the positioning attachment 22and the infusion ports 25 can be arranged non-circumferentially,preferably linearly on one side for focal ablation and delivery ofvapor. The positioning attachment 22 is one of an inflatable balloon, awire mesh disc with or without an insulated membrane covering the disc,a cone shaped attachment, a ring shaped attachment or a freeformattachment designed to fit the desired hollow body organ or hollow bodypassage, as further described below. Optional infrared, electromagnetic,acoustic or radiofrequency energy emitters and sensors 28 areincorporated to measure the dimensions of the hollow organ.

The vapor ablation catheter may also comprise an optional coaxial sheet27 to restrain the positioning attachment 22 in a manner comparable to acoronary metal stent. In one embodiment, the sheet is made of memorymetal or memory material with a compressed linear form and anon-compressed form in the shape of the positioning attachment.Alternatively, the channel of an endoscope may perform the function ofrestraining the positioning attachment 22 by, for example, acting as aconstraining sheath. Optional sensor 26 is deployed on the catheter tomeasure changes associated with vapor delivery or ablation. The sensoris one of temperature, pressure, photo or chemical sensor.

Optionally, one or more, infrared, electromagnetic, acoustic orradiofrequency energy emitters and sensors 28 can measure the dimensionsof the hollow organ. The infrared, electromagnetic, acoustic orradiofrequency energy is emitted from the emitter 28 and is reflectedback from the tissue to the detector in the emitter 28. The reflecteddata can be used to determine the dimension of the hollow cavity. Themeasurement is performed at one or multiple points to get an accurateestimate of the dimension of the hollow organ. The data can also be usedto create a topographic representation of the hollow organ. Additionaldata from diagnostic tests can be used to validate or add to the datafrom the above measurements. FIG. 2E illustrates a catheter 21 of theablation device, in accordance with another embodiment of the presentspecification. The catheter 21 is similar to that described withreference to FIG. 2D, however, the catheter 21 of FIG. 2E additionallyincludes at least one port 19 for the delivery of a conductive medium31. In one embodiment, the conductive medium 31 is injected into thehollow tissue or organ prior to the introduction of the ablative agent29. Once the tissue has been filled to an appropriate level with theconductive medium 31, ablative agent 29 is then delivered into theconductive medium 31 filled tissue. The conductive medium 31 acts toevenly distribute the ablative agent 29, resulting in more consistentand effective ablation of the target tissue.

FIG. 2F illustrates a catheter 21 of the ablation device, in accordancewith yet another embodiment of the present specification. The catheter21 is similar to that described with reference to FIG. 2E, however, thecatheter 21 of FIG. 2F additionally includes at least one port 30 forthe removal via suction of the natural contents of the hollow tissue ororgan. In one embodiment, the natural contents of the hollow tissue ororgan are removed prior to the introduction of the conductive medium 31or the ablative agent 29.

In another embodiment, as depicted in FIG. 2E, wherein the catheterincludes at least one port 25 for the delivery of ablative agent and atleast one other port 19 for the delivery of a conductive medium, thenatural contents of the hollow tissue or organ can be removed viasuction using the ablative agent delivery port 25. In anotherembodiment, as depicted in FIG. 2E, wherein the catheter includes atleast one port 25 for the delivery of ablative agent and at least oneother port 19 for the delivery of a conductive medium, the naturalcontents of the hollow tissue or organ can be removed via suction usingthe conductive medium delivery port 19. In yet another embodiment, asdepicted in FIG. 2D, the conductive medium can be delivered, and, thenatural contents of the hollow tissue or organ can be removed viasuction, using the ablative agent delivery port 25. In variousembodiments, after ablation of the target tissue(s), the remainingcontents of the hollow tissue or organ are removed via suction using oneor more of the ports described above.

In various embodiments, with respect to the catheters depicted in FIGS.2A-2F, the ablative agent can be any one of steam, liquid nitrogen, orany other suitable ablative agent.

FIG. 2G is a flow chart listing the steps involved in a hollow tissue ororgan ablation process using the ablation device, in accordance with oneembodiment of the present specification. At step 202, an endoscope isinserted into a patient. An ablation device comprising a catheter inaccordance with one embodiment of the present specification, is advancedthrough a working channel of the endoscope and to a target tissue atstep 204. At step 206, the distal end or tip of the catheter is insertedinto the target hollow tissue or organ. Then, at step 208, suction isapplied at the proximal end of the catheter to remove the naturalcontents of the hollow tissue or organ. A conductive medium is theninjected, at step 210, into the hollow tissue or organ via at least oneport on the distal end of the catheter. At step 212, an ablative agentis delivered into the conductive medium for ablation of the targettissue. At step 214, the remaining contents of the tissue, includingconductive medium and ablative agent, are removed via suction using thecatheter. In another embodiment, step 214 is optional, and the remainingcontents of the hollow tissue or organ are reabsorbed by the body. Inanother embodiment, the removal of the natural contents of the hollowtissue or organ at step 208 is optional, and the procedure movesdirectly to the injection of conductive medium at step 210 from enteringthe target tissue with the catheter at step 206. Optionally, in someembodiments, the natural contents of the hollow organ can be used as theconductive media.

FIG. 2H illustrates an ablation device 220 in the form of a catheter 221extending from a conventional handle 222, in accordance with anembodiment of the present specification. The catheter 221 is of a typeas described above and extends from and attaches to the handle 222. Inone embodiment, the catheter 221 is insulated to protect the user fromburns that could result from hot vapor heating the catheter. In oneembodiment, the catheter is composed of a material that will ensure thatthe outer temperature of the catheter will remain below 60° C. duringuse. The handle 222 includes a pressure resistant port at the point ofattachment with the catheter 221. The handle 222 also includes a flowchannel within that directs vapor through to the catheter 221.

In one embodiment, the snare handle 222 includes a single attachmentport 223 for the connection of a vapor stream and an RF feed. In anotherembodiment (not shown), the snare handle includes two separateattachment ports for the connection of a vapor stream and an RF feed.The attachment port 223 interfaces with the vapor supply cord viapressure-resistant connectors. In one embodiment, the connectors are ofa luer lock type. In one embodiment, the catheter 221 is a dual lumencatheter. The first lumen serves to deliver vapor to the site ofablation. In one embodiment, the vapor is released through small ports224 positioned proximate the distal end of the catheter 221. The distalend of the catheter 221 is designed so that it can puncture the tissueto deliver vapor to the desired depth and location within the targettissue. In one embodiment, the distal end of the catheter 221 tapers toa point. The second lumen houses the electrode used for RF ablation. Inone embodiment, the delivery of vapor or RF waves is achieved throughthe use of a microprocessor. In another embodiment, the user can releasevapor or subject the target tissue to RF waves by the use of actuators(not shown) on the handle 222. In one embodiment, the catheter hasvarying or differential insulation along its length. In one embodiment,the ablation device 220 includes a mechanism in which a snare to graspthe tissue to be ablated and sizing the tissue in the snare is used todetermine the amount of vapor to be delivered.

FIG. 2I illustrates a cross section of an ablation device 227 in theform of a catheter 231 extending from a conventional handle 232 with apre-attached cord 235, in accordance with another embodiment of thepresent specification. The cord 235 attaches directly to the vapordelivery system, eliminating one interface between the system and theablation device and thereby decreasing the chance of system failure as aresult of disconnection. In this embodiment, the handle 232 includes aseparate attachment port (not shown) for the RF or an electric feed.

FIG. 2J illustrates an ablation device 229 in the form of a catheter 241extending from a conventional esophageal probe 226, in accordance withan embodiment of the present specification. In one embodiment, thecatheter 241 is insulated and receives vapor from a flow channelcontained within the probe 226. The catheter 241 includes a multitude ofsmall ports 244 for the delivery of vapor to the target tissue. Thedelivery of vapor is controlled by a microprocessor. In one embodiment,the catheter 241 also includes two inflatable balloons 228, one at itsdistal end beyond the last vapor port 244, and one at its proximal end,proximate the catheter's 241 attachment to the probe 226. All vaporports are positioned between these two balloons. Once the device 229 isinserted within the esophagus, the balloons 228 are inflated to keep thecatheter 241 positioned and to contain the vapor within the desiredtreatment area. In one embodiment, the balloons must be separated fromthe ablation region by a distance of greater than 0 mm, preferably 1 mmand ideally 1 cm. In one embodiment, the diameter of each balloon wheninflated is in the range of 10 to 100 mm, preferably 15-40 mm, althoughone of ordinary skill in the art would appreciate that the precisedimensions are dependent on the size of the patient's esophagus.

In one embodiment, the catheter 241 attached to the esophageal probe 226is a dual lumen catheter. The first lumen serves to deliver vapor to thesite of ablation as described above. The second lumen houses theelectrode used for RF ablation.

In various embodiments, ablation therapy provided by the vapor ablationsystems of the present specification is delivered to achieve thefollowing general therapeutic endpoints: maintain a tissue temperaturebetween 45° C. and 100° C. for a time period lasting longer than 1 sec;maintain a tissue temperature at 100° C. or less to cause coagulation ofintracellular proteins without carbonization of intracellular sugars;exert a pressure on a tissue to be ablated equal to or less than 125% ofa pre-treatment pressure of the tissue; and exert a pressure on a tissueto be ablated which is less than a patient's mean arterial pressure soas not to impede perfusion to the tissue.

FIG. 3A illustrates the ablation device placed in an uppergastrointestinal tract with Barrett's esophagus to selectively ablatethe Barrett's tissue, in accordance with an embodiment of the presentspecification. The upper gastrointestinal tract comprises Barrett'sesophagus 31, gastric cardia 32, gastroesophageal junction 33 anddisplaced squamo-columnar junction 34. The area between thegastroesophageal junction 33 and the displaced squamo-columnar junction34 is Barrett's esophagus 31, which is targeted for ablation. Distal tothe cardia 32 is the stomach 35 and proximal to the cardia 32 is theesophagus 36. The ablation device is passed into the esophagus 36 andthe positioning device 11 is placed in the gastric cardia 32 abuttingthe gastroesophageal junction 33. This affixes the ablation catheter 10and its ports 12 in the center of the esophagus 36 and allows foruniform delivery of the ablative agent 21 to the Barrett's esophagus 31.

In one embodiment, the positioning device is first affixed to ananatomical structure, not being subjected to ablation, before ablationoccurs. Where the patient is undergoing circumferential ablation orfirst time ablation, the positioning attachment is preferably placed inthe gastric cardia, abutting the gastroesophageal junction. Where thepatient is undergoing a focal ablation of any residual disease, it ispreferable to use the catheter system shown in FIG. 4B, as discussedbelow. In one embodiment, the positioning attachment must be separatedfrom the ablation region by a distance of greater than 0 mm, preferably1 mm and ideally 1 cm. In one embodiment, the size of the positioningdevice is in the range of 10 to 100 mm, preferably 20-40 mm, althoughone of ordinary skill in the art would appreciate that the precisedimensions are dependent on the size of the patient's esophagus.

The delivery of ablative agent 21 through the infusion port 12 iscontrolled by the microprocessor 15 coupled with the ablation device.The delivery of ablative agent is guided by predetermined programmaticinstructions, depending on the tissue to be ablated and the depth ofablation required. In one embodiment, the target procedural temperaturewill need to be between −100 degrees Celsius and 200 degrees Celsius,preferably between 50 degrees Celsius and 75 degrees Celsius, as furthershown in the dosimetery table below. In one embodiment, esophagealpressure should not exceed 5 atm, and is preferably below 0.5 atm. Inone embodiment, the target procedural temperature is achieved in lessthan 1 minute, preferably in less than 5 seconds, and is capable ofbeing maintained for up to 10 minutes, preferably 1 to 10 seconds, andthen cooled close to the body temperature. One of ordinary skill in theart would appreciate that the treatment can be repeated until thedesired ablation effect is achieved.

Optional sensor 17 monitors intraluminal parameters such as temperatureand pressure and can increase or decrease the flow of ablative agent 21through the infusion port 12 to obtain adequate heating or cooling,resulting in adequate ablation. The sensor 17 monitors intraluminalparameters such as temperature and pressure and can increase or decreasethe removal of ablative agent 21 through the optional suction port 13 toobtain adequate heating or cooling resulting in adequate ablation ofBarrett's esophagus 31. FIG. 3B illustrates the ablation device placedin an upper gastrointestinal tract with Barrett's esophagus toselectively ablate the Barrett's tissue, in accordance with anotherembodiment of the present specification. As illustrated in FIG. 3B, thepositioning device 11 is a wire mesh disc. In one embodiment, thepositioning attachment must be separated from the ablation region by adistance of greater than 0 mm, preferably 1 mm and ideally 1 cm. In oneembodiment, the positioning attachment is removably affixed to thecardia or gastroesophageal (EG) junction (for the distal attachment) orin the esophagus by a distance of greater than 0.1 mm, preferably around1 cm, above the proximal most extent of the Barrett's tissue (for theproximal attachment).

FIG. 3B is another embodiment of the Barrett's ablation device where thepositioning element 11 is a wire mesh disc. The wire mesh may have anoptional insulated membrane to prevent the escape of the ablative agent.In the current embodiment, two wire mesh discs are used to center theablation catheter in the esophagus. The distance between the two discsis determined by the length of the tissue to be ablated which, in thiscase, would be the length of the Barrett's esophagus. Optional infrared,electromagnetic, acoustic or radiofrequency energy emitters and sensors18 are incorporated to measure the diameter of the esophagus.

In various embodiments, ablation therapy provided by the vapor ablationsystems of the present specification is delivered to achieve thefollowing therapeutic endpoints for Barrett's esophagus: maintain atissue temperature at 100° C. or less; ablate a mucosa withoutsignificantly damaging a deep submucosa; ablate at least 50% of asurface area of a targeted Barrett's esophagus mucosa such that uponhealing, said Barrett's esophagus mucosa is replaced by normal squamousmucosa; replacement of Barrett's esophagus mucosa with normal squamousmucosa without stricture formation; and ablate at least 50% of a surfacearea of a targeted Barrett's esophagus mucosa with dysplasia such thatupon healing, said Barrett's esophagus mucosa is replaced by normalsquamous mucosa without dysplasia.

In various embodiments, ablation therapy provided by the vapor ablationsystems of the present specification is delivered to achieve thefollowing therapeutic endpoints for esophageal cancer: maintain a tissuetemperature at 100° C. or less; ablate at least 50% of a surface area ofa targeted cancer mucosa to a sufficient depth such that after ablationa cross-sectional area improves by at least 10% relative to apre-treatment cross-sectional area; a patient's dysphagia score improvesby at least 1 grade relative a pre-treatment score; and a tumor volumedecreases by at least 10% relative to a pre-treatment tumor volume.

FIG. 3C is a flowchart illustrating the basic procedural steps for usingthe ablation device, in accordance with an embodiment of the presentspecification. At step 302, a catheter of the ablation device isinserted into an organ which is to be ablated. For example, in order toperform ablation in a Barrett's esophagus of a patient, the catheter isinserted into the Barrett's esophagus via the esophagus of the patient.

At step 304, a positioning element of the ablation device is deployedand organ dimensions are measured. In an embodiment, where thepositioning element is a balloon, the balloon is inflated in order toposition the ablation device at a known fixed distance from the tissueto be ablated. In various embodiments, the diameter of the hollow organmay be predetermined by using radiological tests such as barium X-raysor computer tomography (CT) scan, or by using pressure volume cycle,i.e. by determining volume needed to raise pressure to a fixed level(for example, 1 atm) in a fixed volume balloon. In another embodiment,where the positioning device is disc shaped, circumferential rings areprovided in order to visually communicate to an operating physician thediameter of the hollow organ. In various embodiments of the presentspecification, the positioning device enables centering of the catheterof the ablation device in a non-cylindrical body cavity, and the volumeof the cavity is measured by the length of catheter or a uterine sound.

Optionally, one or more infrared, electromagnetic, acoustic orradiofrequency energy emitters and sensors can be used to measure thedimensions of the hollow organ. The infrared, electromagnetic, acousticor radiofrequency energy is emitted from the emitter and is reflectedback from the tissue to a detector in the emitter. The reflected datacan be used to determine the dimensions of the hollow cavity. Themeasurement can be performed at one or multiple points to get anaccurate estimate of the dimensions of the hollow organ. The data frommultiple points can also be used to create a topographic representationof the hollow organ or to calculate the volume of the hollow organ.

In one embodiment, the positioning attachment must be separated from theports by a distance of 0 mm or greater, preferably greater than 0.1 mm,and more preferably 1 cm. The size of the positioning device depends onthe hollow organ being ablated and ranges from 1 mm to 10 cm. In oneembodiment, the diameter of the positioning element is between 0.01 mmand 100 mm. In one embodiment, the first positioning element comprises acircular body with a diameter between 0.01 mm and 10 cm.

At step 306, the organ is ablated by automated delivery of an ablativeagent, such as steam, via infusion ports provided on the catheter. Thedelivery of the ablative agent through the infusion ports is controlledby a microprocessor coupled with the ablation device. The delivery ofablative agent is guided by predetermined programmatic instructionsdepending on the tissue to be ablated and the depth of ablationrequired. In an embodiment of the present specification where theablative agent is steam, the dose of the ablative agent is determined byconducting dosimetery study to determine the dose to ablate endometrialtissue. The variable that enables determination of total dose ofablative agent is the volume (or mass) of the tissue to be treated whichis calculated by using the length of the catheter and diameter of theorgan (for cylindrical organs). The determined dose of ablative agent isthen delivered using a micro-processor controlled steam generator.Optionally, the delivery of the ablative agent can be controlled by theoperator using predetermined dosimetry parameters.

In one embodiment, the dose is provided by first determining what thedisorder being treated is and what the desired tissue effect is, andthen finding the corresponding temperature, as shown in Tables 1 and 2,below.

TABLE 1 Temp in ° C. Tissue Effect 37-40 No significant tissue effect41-44 Reversible cell damage in few hours 45-49 Irreversible cell damageat shorter intervals 50-69 Irreversible cell damage -ablation necrosisat shorter intervals 70 Threshold temp for tissue shrinkage, H-bondbreakage 70-99 Coagulation and Hemostasis 100-200 Desiccation andCarbonization of tissue >200  Charring of tissue glucose

TABLE 2 Disorder Max. Temp in ° C. ENT/Pulmonary Nasal Polyp 60-80Turbinectomy 70-85 Bullous Disease 70-85 Lung Reduction 70-85Genitourinary Uterine Menorrhagia 80-90 Endometriosis 80-90 UterineFibroids  90-100 Benign Prostatic Hypertrophy  90-100 GastroenterologyBarrett's Esophagus 60-75 Esophageal Dysplasia 60-80 Vascular GIDisorders 55-75 Flat Polyps 60-80

In addition, the depth of ablation desired determines the holding timeat the maximum temperature. For superficial ablation (Barrett), theholding time at the maximum temperature is very short (flash burn) anddoes not allow for heat to transfer to the deeper layers. This willprevent damage to deeper normal tissue and hence prevent patientdiscomfort and complications. For deeper tissue ablation, the holdingtime at the maximum temperature will be longer, thereby allowing theheat to percolate deeper.

The prior art describes the need to provide an expansion mechanism toopen a collapsed hollow organ to provide uniform ablation. This isroutinely performed using balloons, shaped meshes or other structures.It is desirable to provide a method for ablation not requiring anexpansion mechanism. FIG. 3D is a flowchart listing the steps of oneembodiment of a method of providing vapor to a hollow organ where thevapor heats the air in the hollow organ, thus expanding the organ andeliminating the mucosal folds for uniform delivery of ablative energy.At step 310, an ablation device is inserted into a patient. The distalend of the device is positioned in a lumen of a hollow organ targetedfor ablation therapy at step 311. Then, at step 312, vapor is deliveredto the lumen at a predetermined temperature and pressure to causeadequate expansion of the hollow organ and target tissue for uniformdelivery of the ablative agent without over expanding the hollow organand causing a tear or perforation.

The prior art also describes the need for an occlusive mechanism toprevent the flow of ablative energy out of the target tissue region. Itis desirable to provide a method for ablation which does not require theuse of an occlusive agent to prevent the flow of energy beyond thetargeted tissue to prevent damage to healthy tissue. FIG. 3E is aflowchart listing the steps of one embodiment of a method of providingvapor to a hollow organ wherein the vapor does not escape substantiallybeyond the target tissue to be ablated. At step 315, an ablation deviceis inserted into a patient. The distal end of the device is positionedin a lumen of a hollow organ targeted for ablation therapy at step 316.Then, at step 317, the vapor is delivered to the lumen at apredetermined temperature and pressure to cause localization andcondensation of the vapor in the target tissue without escape of thevapor substantially beyond the target tissue, thus preventingsignificant damage to nearby normal tissue.

FIG. 3F illustrates an esophageal ablation catheter 320 with ventingtubes 338, 339 in accordance with one embodiment of the presentspecification. The catheter 320 includes an elongate body 321 with aproximal end and a distal end. In one embodiment, the catheter body 321includes an inner lumen 322 and an outer lumen 323. The inner lumen 322is separated from the outer lumen 323 by a thermally semi-permeable wall324 which allows a portion of the thermal energy to pass from the innerlumen 322 to the outer lumen 323. The catheter also includes at leastone positioning balloon at its distal end. In the embodiment depicted inFIG. 3F, the catheter 320 includes two positioning balloons 325, 326 atits distal end with a plurality of delivery ports 327 located on thecatheter body 321 between the two balloons 325, 326. The delivery ports327 are in fluid communication with the inner lumen 322. An ablativeagent 328 is introduced into the inner lumen 322 at the proximal end ofthe catheter 320 and exits through the delivery ports 327 into anesophagus for ablation. In one embodiment, the ablative agent 328 issteam. Air 329 is introduced into the outer lumen 323 at the proximalend of the catheter 320 and exits through inflation ports 330 into theballoons 325, 326 to inflate said balloons 325, 326. It is undesirableto form a tight seal during delivery of thermal ablation as a tight sealprevents the escape of heated air and can lead to thermal expansionrelated injury to an organ. Specifically, the tissue area between theinflated balloons 325, 326 can be damaged if the heated air cannotescape and causes thermal expansion injury. Therefore, in someembodiments, the catheter 320 includes venting tubes 338, 339 to allowthe expanded air or extra vapor 337 to vent out passively. The ventingtubes 338, 339 allow for the escape of hot air or excess vapor 337 froman area between the two balloons 325, 326 to a space distal to balloon326 or proximal to balloon 325. In some embodiments, the venting tubes338, 339 include a one way valve for unidirectional flow. In someembodiments, the one way valves include a pressure threshold and openonce the pressure threshold is reached.

FIG. 3G illustrates an esophageal ablation catheter 340 with a ventingtube 349 in accordance with another embodiment of the presentspecification. The catheter 340 functions similarly to the esophagealablation catheter of FIG. 3F but differs in that the inner lumen 332does not extend distally through the catheter body 331 as far as theinner lumen 321 of catheter 320 depicted in FIG. 3F. The distal end ofcatheter body 331 rather includes a venting tube 349 to allow for theescape of expanded air or extra vapor 347 from an area between the twoballoons 335, 336 to a space distal to balloon 336. In some embodiments,the venting tube 349 includes a one way valve for unidirectional flow.In some embodiments, the one way valve includes a pressure threshold andopens once the pressure threshold is reached.

FIG. 4A illustrates the ablation device placed in a colon to ablate aflat colon polyp, in accordance with an embodiment of the presentspecification. The ablation catheter 10 is passed through a colonoscope40. The positioning device 11 is placed proximal, with respect to thepatient's GI tract, to a flat colonic polyp 41 which is to be ablated,in the normal colon 42. The positioning device 11 is one of aninflatable balloon, a wire mesh disc with or without an insulatedmembrane covering the disc, a cone shaped attachment, a ring shapedattachment or a freeform attachment designed to fit the colonic lumen.The positioning device 11 has the catheter 10 located toward theperiphery of the positioning device 11 placing it closer to the polyp 41targeted for non-circumferential ablation. Hence, the positioning device11 fixes the catheter to the colon 42 at a predetermined distance fromthe polyp 41 for uniform and focused delivery of the ablative agent 21.The delivery of ablative agent 21 through the infusion port 12 iscontrolled by the microprocessor 15 attached to the ablation device anddepends on tissue and the depth of ablation required. The delivery ofablative agent 21 is guided by predetermined programmatic instructionsdepending on the tissue to be ablated and the area and depth of ablationrequired. Optional infrared, electromagnetic, acoustic or radiofrequencyenergy emitters and sensors 18 are incorporated to measure the diameterof the colon. The ablation device allows for focal ablation of diseasedpolyp mucosa without damaging the normal colonic mucosa located awayfrom the catheter ports.

In one embodiment, the positioning attachment must be separated from theablation region by a distance of greater than 0.1 mm, ideally more than5 mm. In one embodiment, the positioning element is proximal, withrespect to the patient's GI tract, to the colon polyp. For thisapplication, the embodiment shown in FIG. 4B would be preferred.

FIG. 4B illustrates the ablation device placed in a colon 42 to ablate aflat colon polyp 41, in accordance with another embodiment of thepresent specification. As illustrated in FIG. 4B, the positioning device11 is a conical attachment at the tip of the catheter 10. The conicalattachment has a known length ‘l’ and diameter ‘d’ that is used tocalculate the amount of thermal energy needed to ablate the flat colonpolyp 41. Ablative agent 21 is directed from the infusion port 12 topolyp 41 by the positioning device 11. In one embodiment, thepositioning attachment 11 must be separated from the ablation region bya distance of greater than 0.1 mm, preferably 1 mm and more preferably 1cm. In one embodiment, the length ‘l’ is greater than 0.1 mm, preferablybetween 5 and 10 mm. In one embodiment, diameter ‘d’ depends on the sizeof the polyp and can be between 1 mm and 10 cm, preferably 1 to 5 cm.Optional infrared, electromagnetic, acoustic or radiofrequency energyemitters and sensors 18 are incorporated to measure the diameter of thecolon. This embodiment can also be used to ablate residual neoplastictissue at the edges after endoscopic snare resection of a large sessilecolon polyp.

In some instances, it is desirable to ablate a portion of a patient'sduodenal mucosa for the treatment of various gastrointestinal (GI)disorders. However, it is not advisable to ablate or inflict trauma uponthe patient's nearby ampulla of Vater during such a procedure. Trauma tothe ampulla increases the risk of causing pancreatitis, pancreatic orbiliary stricture, or cholangitis. FIG. 4C illustrates an ablationcatheter 420 having an ampullary shield 423 inserted in the duodenum 402of a patient, in accordance with one embodiment of the presentspecification. Also depicted are the patient's gall bladder 404, commonbile duct 406, pancreas 408, and pancreatic duct 410. The catheter 420is passed through an endoscope 421 to position the distal end of thecatheter 420 within the duodenum 402. In one embodiment, first andsecond positioning elements, or balloons 422, 424 on the catheter 420assist in positioning the catheter 420 within the patient'santroduodenal area. The ampullary shield 423, attached to the catheter420, covers the patient's ampulla of Vater 412 and prevents ablativeagent 425 from coming into contact with said ampulla 412. In variousembodiments, the ampullary shield 423 is composed of silicone andapproximates a rectangular, square, circular, or oval shape.

FIG. 4D is a flowchart listing the steps in one embodiment of a methodof using the ablation catheter having an ampullary shield of FIG. 4C. Atstep 430, an endoscope is inserted into a patient's gastrointestinal(GI) tract. The catheter is passed through the endoscope and its distalend advanced into the patient's antroduodenal region at step 431. Then,at step 432, at least one positioning balloon is deployed in saidantroduodenal region. The ampullary shield is deployed at step 433 tocover the patient's ampullary region. Ablative agent is then deliveredat step 434 to ablate a portion of the duodenal mucosa without ablatingor damaging the patient's ampulla of Vater.

FIG. 4E illustrates deflated 440 d, lateral inflated 4401, and frontalinflated 440 f views of an ablation catheter 440 having an insulatingmembrane 449 for duodenal ablation, in accordance with one embodiment ofthe present specification. In some embodiments, the catheter 440comprises a water-cooled catheter having a proximal inflatable balloon442 and a distal inflatable balloon 444 with an insulating membrane 449which extends from a proximal end of the proximal balloon 442 to adistal end of the distal balloon 444. A plurality of vapor deliveryports 443 are positioned on the catheter 440 between the proximalballoon 442 and distal balloon 444. Once the balloons 442, 444 areinflated, as depicted in lateral view 4401, the stretching of theinsulating membrane 449 between the balloons 442, 444 causes thecatheter 440 to bow, helping to position the insulating membrane overthe ampulla of vater, thereby providing a protective shield over theampulla during vapor ablation therapy.

In various embodiments, ablation therapy provided by the vapor ablationsystems of the present specification is delivered to achieve thefollowing therapeutic endpoints for duodenal ablation: maintain a tissuetemperature at 100° C. or less; ablate at least 50% of a surface area ofa duodenal mucosa; ablate a duodenal mucosa without significant ablationof an ampullary mucosa; reduce fasting blood glucose by at least 5%relative to pre-treatment fasting blood glucose; reduce HbA1C by atleast 5% relative to pre-treatment HbA1C; reduce total body weight by atleast 1% relative to pre-treatment body weight; reduce excess bodyweight by at least 3% relative to pre-treatment excess body weight;reduce mean blood pressure by at least 3% relative to pre-treatment meanblood pressure; and reduce total cholesterol by at least 3% relative topre-treatment total cholesterol.

FIG. 5A illustrates the ablation device with a coaxial catheter design,in accordance with an embodiment of the present specification. Thecoaxial design has a handle 52 a, an infusion port 53 a, an inner sheath54 a and an outer sheath 55 a. The outer sheath 55 a is used toconstrain the positioning device 56 a in the closed position andencompasses ports 57 a. FIG. 5B shows a partially deployed positioningdevice 56 b, with the ports 57 b still within the outer sheath 55 b. Thepositioning device 56 b is partially deployed by pushing the catheter 54b out of sheath 55 b.

FIG. 5C shows a completely deployed positioning device 56 c. Theinfusion ports 57 c are out of the sheath 55 c. The length ‘l’ of thecatheter 54 c that contains the infusion ports 57 c and the diameter ‘d’of the positioning element 56 c are predetermined/known and are used tocalculate the amount of thermal energy needed. FIG. 5D illustrates aconical design of the positioning element. The positioning element 56 dis conical with a known length ‘l’ and diameter ‘d’ that is used tocalculate the amount of thermal energy needed for ablation. FIG. 5Eillustrates a disc shaped design of the positioning element 56 ecomprising circumferential rings 59 e. The circumferential rings 59 eare provided at a fixed predetermined distance from the catheter 54 eand are used to estimate the diameter of a hollow organ or hollowpassage in a patient's body.

FIG. 6 illustrates an upper gastrointestinal tract with a bleedingvascular lesion being treated by the ablation device, in accordance withan embodiment of the present specification. The vascular lesion is avisible vessel 61 in the base of an ulcer 62. The ablation catheter 63is passed through the channel of an endoscope 64. The conicalpositioning element 65 is placed over the visible vessel 61. The conicalpositioning element 65 has a known length ‘l’ and diameter ‘d’, whichare used to calculate the amount of thermal energy needed forcoagulation of the visible vessel to achieve hemostasis. The conicalpositioning element has an optional insulated membrane that preventsescape of thermal energy or vapor away from the disease site.

In one embodiment, the positioning attachment must be separated from theablation region by a distance of greater than 0.1 mm, preferably 1 mmand more preferably 1 cm. In one embodiment, the length ‘l’ is greaterthan 0.1 mm, preferably between 5 and 10 mm. In one embodiment, diameter‘d’ depends on the size of the lesion and can be between 1 mm and 10 cm,preferably 1 to 5 cm.

FIG. 7A illustrates endometrial ablation being performed in a femaleuterus by using the ablation device, in accordance with an embodiment ofthe present specification. A cross-section of the female genital tractcomprising a vagina 70, a cervix 71, a uterus 72, an endometrium 73,fallopian tubes 74, ovaries 75 and the fundus of the uterus 76 isillustrated. A catheter 77 of the ablation device is inserted into theuterus 72 through the cervix 71 at the cervical os. In an embodiment,the catheter 77 has two positioning elements, a conical positioningelement 78 and a disc shaped positioning element 79. The positioningelement 78 is conical with an insulated membrane covering the conicalpositioning element 78. The conical element 78 positions the catheter 77in the center of the cervix 71 and the insulated membrane prevents theescape of thermal energy or ablative agent out the cervix 71 through theos. The second disc shaped positioning element 79 is deployed close tothe fundus of the uterus 76 positioning the catheter 77 in the middle ofthe cavity. An ablative agent 778 is passed through infusion ports 777for uniform delivery of the ablative agent 778 into the uterine cavity.Predetermined length ‘l’ of the ablative segment of the catheter anddiameter ‘d’ of the positioning element 79 allows for estimation of thecavity size and is used to calculate the amount of thermal energy neededto ablate the endometrial lining. In one embodiment, the positioningelements 78, 79 also act to move the endometrial tissue away from theinfusion ports 777 on the catheter 77 to allow for the delivery ofablative agent. Optional temperature sensors 7 deployed close to theendometrial surface are used to control the delivery of the ablativeagent 778. Optional topographic mapping using multiple infrared,electromagnetic, acoustic or radiofrequency energy emitters and sensorscan be used to define cavity size and shape in patients with anirregular or deformed uterine cavity due to conditions such as fibroids.Additionally, data from diagnostic testing can be used to ascertain theuterine cavity size, shape, or other characteristics.

In an embodiment, the ablative agent is vapor or steam which contractson cooling. Steam turns to water which has a lower volume as compared toa cryogen that will expand or a hot fluid used in hydrothermal ablationwhose volume stays constant. With both cryogens and hot fluids,increasing energy delivery is associated with increasing volume of theablative agent which, in turn, requires mechanisms for removing theagent, otherwise the medical provider will run into complications, suchas perforation. However, steam, on cooling, turns into water whichoccupies significantly less volume; therefore, increasing energydelivery is not associated with an increase in volume of the residualablative agent, thereby eliminating the need for continued removal. Thisfurther decreases the risk of leakage of the thermal energy via thefallopian tubes 74 or the cervix 71, thus reducing any risk of thermalinjury to adjacent healthy tissue.

In one embodiment, the positioning attachment must be separated from theablation region by a distance of greater than 0.1 mm, preferably 1 mmand more preferably 1 cm. In another embodiment, the positioningattachment can be in the ablated region as long as it does not cover asignificant surface area. For endometrial ablation, 100% of the tissuedoes not need to be ablated to achieve the desired therapeutic effect.

In one embodiment, the preferred distal positioning attachment is anuncovered wire mesh that is positioned proximate to the mid body region.In one embodiment, the preferred proximal positioning device is acovered wire mesh that is pulled into the cervix, centers the device,and occludes the cervix. One or more such positioning devices may behelpful to compensate for the anatomical variations in the uterus. Theproximal positioning device is preferably oval, with a long axis between0.1 mm and 10 cm (preferably 1 cm to 5 cm) and a short axis between 0.1mm and 5 cm (preferably 0.5 cm to 1 cm). The distal positioning deviceis preferably circular with a diameter between 0.1 mm and 10 cm,preferably 1 cm to 5 cm.

In another embodiment, the catheter is a coaxial catheter comprising anexternal catheter and an internal catheter wherein, upon insertion, thedistal end of the external catheter engages and stops at the cervixwhile the internal extends into the uterus until its distal end contactsthe fundus of the uterus. The length of the internal catheter that haspassed into the uterus is then used to measure the depth of the uterinecavity and determines the amount of ablative agent to use. Ablativeagent is then delivered to the uterine cavity via at least one port onthe internal catheter. In one embodiment, during treatment,intracavitary pressure within the uterus is kept below 100 mm Hg. In oneembodiment, the coaxial catheter further includes a pressure sensor tomeasure intracavitary pressure. In one embodiment, the coaxial catheterfurther includes a temperature sensor to measure intracavitarytemperature. In one embodiment, the ablative agent is steam and thesteam is released from the catheter at a pressure of less than 100 mmHg. In one embodiment, the steam is delivered with a temperature between90 and 100° C.

FIG. 7B is an illustration of a coaxial catheter 720 used in endometrialtissue ablation, in accordance with one embodiment of the presentspecification. The coaxial catheter 720 comprises an inner catheter 721and outer catheter 722. In one embodiment, the inner catheter 721 hasone or more ports 723 for the delivery of an ablative agent 724. In oneembodiment, the ablative agent is steam. In one embodiment, the outercatheter 722 has multiple fins 725 to engage the cervix to prevent theescape of vapor out of the uterus and into the vagina. In oneembodiment, the fins are composed of silicone. In one embodiment, theouter catheter 722 includes a luer lock 726 to prevent the escape ofvapor between the inner catheter 721 and outer catheter 722. In oneembodiment, the inner catheter 721 includes measurement markings 727 tomeasure the depth of insertion of the inner catheter 721 beyond the tipof the outer catheter 722. Optionally, in various embodiments, one ormore sensors 728 are incorporated into the inner catheter 721 to measureintracavitary pressure or temperature.

FIG. 7C is a flow chart listing the steps involved in an endometrialtissue ablation process using a coaxial ablation catheter, in accordancewith one embodiment of the present specification. At step 702, thecoaxial catheter is inserted into the patient's vagina and advanced tothe cervix. Then, at step 704, the coaxial catheter is advanced suchthat the fins of the outer catheter engage the cervix, effectivelystopping advancement of the outer catheter at that point. The innercatheter is then advanced, at step 706, until the distal end of theinternal catheter contacts the fundus of the uterus. The depth ofinsertion is then measured using the measurement markers on the internalcatheter at step 708, thereby determining the amount of ablative agentto use in the procedure. At step 710, the luer lock is tightened toprevent any escape of vapor between the two catheters. The vapor is thendelivered, at step 712, through the lumen of the inner catheter and intothe uterus via the delivery ports on the internal catheter to ablate theendometrial tissue.

FIG. 7D is an illustration of a bifurcating coaxial catheter 730 used inendometrial tissue ablation, in accordance with one embodiment of thepresent specification. The catheter 730 includes a first elongate shaft732 having a proximal end, a distal end and a first lumen within. Thefirst lumen splits in the distal end to create a coaxial shaft 733. Thedistal end of the first shaft 732 also includes a first positioningelement, or cervical plug 734, that occludes a patient's cervix. Thecatheter 730 bifurcates as it extends distally from the cervical plug734 to form a second catheter shaft 735 and a third catheter shaft 736.The second and third catheter shafts 735, 736 each include a proximalend, a distal end, and a shaft body having one or more vapor deliveryports 737. The second and third catheter shafts 735, 736 include secondand third lumens respectively, for the delivery of ablative agent. Thedistal ends of the second and third catheter shafts 735, 736 includesecond and third positioning elements, or fallopian tube plugs 738, 739respectively, designed to engage a patient's fallopian tubes during anablation therapy procedure and prevent the escape of ablative energy.The fallopian tube plugs 738, 739 also serve to position the second andthird shafts 735, 736 respectively, in an intramural portion or isthmusof a patient's fallopian tube. The second and third catheter shafts 735,736 are independently coaxially extendable and the length of each shaft735, 736 is used to determine the dimension of a patient's endometrialcavity. An ablative agent 740 travels through the first catheter shaft732, through both second and third catheter shaft 735, 736, and out thevapor delivery ports 737 and into the endometrial cavity to ablateendometrial tissue.

FIG. 7E is a flowchart listing the steps of a method of using theablation catheter of FIG. 7D to ablate endometrial tissue, in accordancewith one embodiment of the present specification. At step 743, thecoaxial catheter is inserted into a patient's cervix and the cervix isengaged with the cervical plug. The catheter is then advanced until eachfallopian tube plug is proximate a fallopian tube opening at step 744.Each fallopian tube is then engaged with a fallopian tube plug at step745 and the dimensions of the endometrial cavity are measured. Themeasurements are based on the length of each catheter shaft that hasbeen advanced. At step 746, the measured dimensions are used tocalculate the amount of ablative agent needed to carry out the ablation.The calculated dose of ablative agent is then delivered through thecatheter shafts and into the endometrial cavity to produce the desiredendometrial ablation at step 747.

FIG. 7F is an illustration of a bifurcating coaxial catheter 750 withexpandable elements 751, 753 used in endometrial tissue ablation, inaccordance with one embodiment of the present specification. Similar tothe catheter 730 of FIG. 7D, the catheter 750 depicted in FIG. 7Fincludes a first elongate coaxial shaft 752 having a proximal end, adistal end and a first lumen within. The first lumen splits in thedistal end to create a coaxial shaft 749. The distal end of the firstshaft 752 also includes a first positioning element, or cervical plug754, that occludes a patient's cervix. The catheter 750 bifurcates as itextends distally from the cervical plug 754 to form a second cathetershaft 755 and a third catheter shaft 756. The second and third cathetershafts 755, 756 each include a proximal end, a distal end, and acatheter shaft body having one or more vapor delivery ports 757. Thesecond and third catheter shafts 755, 756 include second and thirdlumens respectively, for the delivery of ablative agent. The distal endsof the second and third catheter shafts 755, 756 include second andthird positioning elements, or fallopian tube plugs 758, 759respectively, designed to engage a patient's fallopian tubes during anablation therapy procedure and prevent the escape of ablative energy.The fallopian tube plugs 758, 759 also serve to position the second andthird shafts 755, 756 respectively, in an intramural portion or isthmusof a patient's fallopian tube. The second and third catheter shafts 755,756 are independently coaxially extendable and the length of eachcatheter shaft 755, 756 is used to determine the dimension of apatient's endometrial cavity.

The catheter 750 further includes a first expandable member or balloon751 and a second expandable member or balloon 753 comprising a coaxialballoon structure. In one embodiment, the first balloon 751 is acompliant balloon structure and the second balloon 753 is anon-compliant balloon structure shaped to approximate the uterine cavityshape, size or volume. In another embodiment, the second balloon 753 ispartially compliant. In another embodiment, the compliance of the twoballoons 751, 753 is substantially equivalent. The balloons 751, 753 areattached to the second and third catheter shafts 755, 756 along an innersurface of each shaft 755, 756. The first, inner balloon 751 ispositioned within the second, outer balloon 753. The inner balloon 751is designed to be inflated with air and a first volume of the innerballoon 751 is used to measure a dimension of a patient's endometrialcavity. An ablative agent 761 is introduced into the catheter 750 at itsproximal end and travels through the first catheter shaft 752 and intothe second and third catheter shafts 755, 756. The second and thirdcatheter shafts 755, 756 are designed to release ablative energy 762through delivery ports 757 and into a space 760 between the two balloons751, 753. Some of the ablative energy 763 is transferred to the air inthe inner balloon 751, expanding its volume from said first volume to asecond volume, resulting in further expansion of said inner balloon 751to further occlude the patient's endometrial cavity for ideal vapordelivery. In one embodiment, the second volume is less than 25% greaterthan the first volume. The expansion also forces the fallopian tubeplugs 758, 759 to further engage the openings of the fallopian tubes. Aportion of the ablative agent or ablative energy 764 diffuses out of thethermally permeable outer balloon 753 and into the endometrial cavity,ablating the endometrial tissue. In various embodiments, the thermalheating of the air in the balloon occurs either through the walls of theinner balloon, through the length of the catheter, or through both. Inone embodiment, the catheter 750 includes an optional fourth cathetershaft 765 extending from the first catheter shaft 752 and between thesecond and third catheter shaft 755, 756 within the inner balloon 751.Thermal energy from within the fourth catheter shaft 765 is used tofurther expand the inner balloon 751 and assist with ablation.

In one embodiment, the volume of the inner balloon 751 is used tocontrol the pressure exerted by the outer balloon 753 on the wall of theuterus. The pressure in the inner balloon 751 is monitored and air isadded to or removed from the inner balloon 751 to maintain a desirabletherapeutic pressure in the outer balloon 753.

FIG. 7G is an illustration of the catheter 750 of FIG. 7F inserted intoa patient's uterine cavity 766 for endometrial tissue 767 ablation, inaccordance with one embodiment of the present specification. Thecatheter 750 has been inserted with the first shaft 752 extendingthrough the patient's cervix 768 such that the second shaft 755 ispositioned along a first side of the patient's uterine cavity 766 andthe third shaft 756 is positioned along a second side opposite saidfirst side. This positioning deploys the inner balloon 751 and outerballoon 753 between the second and third shafts 755, 756. In thepictured embodiment, the catheter 750 includes an optional fourth shaft765 to further expand the inner balloon 751 with thermal energy andassist with ablation of endometrial tissue 767. In one embodiment, theinner balloon 751 is optional and the outer balloon 753 performs thefunction of both sizing and delivery of the ablative agent. In oneembodiment, the outer balloon includes heat sensitive pores 769 whichare closed at room temperature and open at a temperature higher than thebody temperature. In one embodiment, the pores are composed of a shapememory alloy (SMA). In one embodiment, the SMA is Nitinol. In oneembodiment, the austenite finish (Af) temperature, or temperature atwhich the transformation from martensite to austenite finishes onheating (alloy undergoes a shape change to become an open pore 769), ofthe SMA is greater than 37° C. In other embodiments, the Af temperatureof the SMA is greater than 50° C. but less than 100° C.

FIG. 7H is a flowchart listing the steps of a method of using theablation catheter of FIG. 7F to ablate endometrial tissue, in accordancewith one embodiment of the present specification. At step 780, thecoaxial catheter is inserted into a patient's cervix and the cervix isengaged with the cervical plug. The catheter is then advanced until eachfallopian tube plug is proximate a fallopian tube opening at step 781.Each fallopian tube is then engaged with a fallopian tube plug at step782, which also deploys the coaxial balloons in the endometrial cavity,and the dimensions of the endometrial cavity are measured. Themeasurements are based on the length of each catheter shaft that hasbeen advanced and a first volume needed to expand the inner balloon to apredetermined pressure. At step 783, the inner balloon is inflated tosaid predetermined pressure and a first volume of the inner balloon atsaid pressure is used to calculate the volume of the endometrial cavity.The measured dimensions are then used at step 784 to calculate theamount of ablative agent needed to carry out the ablation. Thecalculated dose of ablative agent is then delivered through the cathetershafts and into the space between the coaxial balloons at step 785. Someof the ablative energy is transmitted into the inner balloon to expandthe inner balloon to a second volume which further expands theendometrial cavity and, optionally, further pushes the fallopian tubeplugs into the fallopian tube openings to prevent the escape of thermalenergy. Another portion of the ablative energy passes through thethermally permeable outer balloon to produce the desired endometrialablation.

In another embodiment, a vapor ablation device for ablation ofendometrial tissue comprises a catheter designed to be inserted througha cervical os and into an endometrial cavity, wherein the catheter isconnected to a vapor generator for generation of vapor and includes atleast one port positioned in the endometrial cavity to deliver the vaporinto the endometrial cavity. The vapor is delivered through the port andheats and expands the air in the endometrial cavity to maintain theendometrial cavity pressure below 200 mm Hg and ideally below 50 mm ofHg. In one embodiment, an optional pressure sensor measures the pressureand maintains the intracavitary pressure at the desired therapeuticlevel, wherein the endometrial cavity is optimally expanded to allow foruniform distribution of ablative energy without the risk of significantleakage of the ablative energy beyond the endometrial cavity and damageto the adjacent normal tissue.

FIG. 7I is an illustration of a bifurcating coaxial catheter 770 used inendometrial tissue ablation, in accordance with another embodiment ofthe present specification. Forming a seal at the cervix is undesirableas it creates a closed cavity, resulting in a rise of pressure whenvapor is delivered into the uterus. This increases the temperature ofthe intrauterine air, causing a thermal expansion and further rise ofintracavitary pressure. This rise in pressure may force the vapor or hotair to escape out of the fallopian tubes, causing thermal injury to theabdominal viscera. This requires for continuous measurement ofintracavitary pressure and active removal of the ablative agent toprevent leakage of thermal energy outside the cavity. Referring to FIG.7I, the catheter 770 includes a coaxial handle 771, a first positioningelement 772, a first bifurcated catheter arm 735 i with a secondpositing element 738 i at its distal end, a second bifurcated catheterarm 736 i with a third positioning element 739 i at its distal end, anda plurality of infusion ports 737 i along each bifurcated catheter arm735 i, 736 i. The catheter 770 also includes a venting tube 776 whichextends through the coaxial handle 771 and through the first positioningelement 772 such that the lumen of a patient's uterus is in fluidcommunication with the outside of the patient's body when the firstpositioning element 772 is in place positioned against a cervix. Thisprevents formation of a tight seal when the catheter 770 is insertedinto the cervix. Since the cervix is normally in a closed position,insertion of any device will inadvertently result in formation of anundesirable seal. The venting tube allows for heated air or extra vapor740 i to vent out as it expands with delivery of vapor and theintracavitary pressure rises. In some embodiments, the venting tubeincludes a valve for unidirectional flow of air.

FIG. 7J is an illustration of a bifurcating coaxial catheter 773 used inendometrial tissue ablation, in accordance with yet another embodimentof the present specification. The catheter 773 includes a coaxial handle774, a first positioning element 775, a first bifurcated catheter arm735 j with a second positing element 738 j at its distal end, a secondbifurcated catheter arm 736 j with a third positioning element 739 j atits distal end, and a plurality of infusion ports 737 j along eachbifurcated catheter arm 735 j, 736 j. The catheter 773 also includes twoventing tubes 791, 792 which extend through the coaxial handle 774 andthrough the first positioning element 775 such that the lumen of apatient's uterus is in fluid communication with the outside of thepatient's body when the first positioning element 775 is in placepositioned against a cervix. This prevents formation of a tight sealwhen the catheter 773 is inserted into the cervix. The venting tubes791, 792 allow for heated air or extra vapor 740 j to vent out as itexpands with delivery of vapor and the intracavitary pressure rises. Insome embodiments, the venting tubes 791, 792 include a valve forunidirectional flow of air.

FIG. 7K is an illustration of a water cooled catheter 700 k used inendometrial tissue ablation, in accordance with one embodiment of thepresent specification. The catheter 700 k comprises an elongate body 701k having a proximal end and a distal end. The distal end includes aplurality of ports 705 k for the delivery of vapor 707 k for tissueablation. A sheath 702 k extends along the body 701 k of the catheter700 k to a point proximal to the ports 705 k.

During use, water 703 k is circulated through the sheath 702 k to coolthe catheter 700 k. Vapor 707 k for ablation and water 703 k for coolingare supplied to the catheter 700 k at its proximal end.

FIG. 7L is an illustration of a water cooled catheter 700 l used inendometrial tissue ablation and positioned in a uterus 707 l of apatient, in accordance with another embodiment of the presentspecification. The catheter 700 l comprises an elongate body 701 l, aproximal end, distal end, and a sheath 702 l covering a proximal portionof the body 701 l. Extending from, and in fluid communication with, thesheath 702 l is a cervical cup 704 l. The catheter 700 l furtherincludes a plurality of ports 706 l at its distal end configured todeliver ablative vapor 708 l to the uterus 707 l. Vapor 708 l issupplied to the proximal end of the catheter 700 l. The ports 706 l arepositioned on the catheter body 701 l distal to the sheath 702 l. Thecervical cup 704 l is configured to cover the cervix 709 l and a distalend of the sheath 702 l extends into the cervical canal 710 l. Water 703l is circulated through the sheath 702 l and cervical cup 704 l to coolthe cervical canal 710 l and/or cervix 709 l while vapor 708 l isdelivered through the vapor delivery ports 706 l to ablate theendometrial lining 711 l.

In various embodiments, ablation therapy provided by the vapor ablationsystems of the present specification is delivered to achieve thefollowing therapeutic endpoints for uterine ablation: maintain a tissuetemperature at 100° C. or less; increase patient's hemoglobin by atleast 5% or at least 1 gm % relative to pre-treatment hemoglobin;decrease menstrual blood flow by at least 5% as measured by menstrualpad weight relative to pre-treatment menstrual blood flow; ablation ofendometrial tissue in a range of 10% to 99%; decrease in duration ofmenstrual flow by at least 5% relative to pre-treatment menstrual flow;decrease in amenorrhea rate by at least 10% relative to pre-treatmentamenorrhea rate; and patient reported satisfaction with uterine ablationprocedure of greater than 25%.

FIG. 7M is an illustration of a water cooled catheter 700 m used incervical ablation, in accordance with one embodiment of the presentspecification, and FIG. 7N is an illustration of the catheter 700 m ofFIG. 7M positioned in a cervix 709 n of a patient. Referring to FIGS. 7Mand 7N simultaneously, the catheter 7M comprises an elongate body 701 m,a proximal end, a distal end, and a water cooled tip 702 m at its distalend. A cervical cup 714 m is attached to the catheter body 701 m andincludes a plurality of ports 706 m which are in fluid communicationwith the proximal end of the catheter 700 m. Vapor 708 m is provided atthe proximal end of the catheter 700 m and is delivered to the cervix709 n via ports 706 m. In an embodiment, the vapor 708 m ablates thetransformation zone 712 n at the cervix 709 n. The water cooled tip 702m of the catheter 700 m cools the cervical canal 710 n during ablation.

FIG. 7O is a flowchart listing the steps involved in cervical ablationperformed using the catheter of FIG. 7M. At step 702 o the distal tip ofthe catheter is inserted into the cervical canal until the cervical cupof the catheter encircles the cervix. Water is circulated through thewater cooled tip to cool the cervical canal at step 704 o. At step 706 ovapor is passed through the vapor delivery ports in the cervical cup toablate the cervix.

In various embodiments, ablation therapy provided by the vapor ablationsystems of the present specification is delivered to achieve thefollowing therapeutic endpoints for cervical ablation: maintain a tissuetemperature at 100° C. or less; ablate a cervical mucosa withoutsignificant injury to the cervical canal; ablate at least 50% of asurface area of a targeted abnormal cervical mucosa such that, uponhealing, said abnormal cervical mucosa is replaced by normal cervicalmucosa; elimination of more than 25% of abnormal cervical mucosa asassessed by colposcopy; and ablate more than 25% of abnormal cervicalmucosa and less than 25% of a total length of a cervical canal.

FIG. 8 illustrates sinus ablation being performed in a nasal passage byusing the ablation device, in accordance with an embodiment of thepresent specification. A cross-section of the nasal passage and sinusescomprising nares 81, nasal passages 82, frontal sinus 83, ethmoid sinus84, and diseased sinus epithelium 85 is illustrated. The catheter 86 isinserted into the frontal sinus 83 or the ethmoid sinus 84 through thenares 81 and nasal passages 82.

In an embodiment, the catheter 86 has two positioning elements, aconical positioning element 87 and a disc shaped positioning element 88.The positioning element 87 is conical and has an insulated membranecovering. The conical element 87 positions the catheter 86 in the centerof the sinus opening 80 and the insulated membrane prevents the escapeof thermal energy or ablative agent through the opening. The second discshaped positioning element 88 is deployed in the frontal sinus cavity 83or ethmoid sinus cavity 84, positioning the catheter 86 in the middle ofeither sinus cavity. The ablative agent 8 is passed through the infusionport 89 for uniform delivery of the ablative agent 8 into the sinuscavity. The predetermined length ‘l’ of the ablative segment of thecatheter and diameter ‘d’ of the positioning element 88 allows forestimation of the sinus cavity size and is used to calculate the amountof thermal energy needed to ablate the diseased sinus epithelium 85.Optional temperature sensors 888 are deployed close to the diseasedsinus epithelium 85 to control the delivery of the ablative agent 8. Inan embodiment, the ablative agent 8 is steam which contracts on cooling.This further decreases the risk of leakage of the thermal energy thusreducing any risk of thermal injury to adjacent healthy tissue. In oneembodiment, the dimensional ranges of the positioning elements aresimilar to those in the endometrial application, with preferred maximumranges being half thereof. Optional topographic mapping using multipleinfrared, electromagnetic, acoustic or radiofrequency energy emittersand sensors can be used to define cavity size and shape in patients withan irregular or deformed nasal cavity due to conditions such as nasalpolyps. In various embodiments, the ablative agent is combined with anantibiotic or anti-inflammatory agent, including a long-acting steroid.

FIG. 9A illustrates bronchial and bullous ablation being performed in apulmonary system by using the ablation device, in accordance with anembodiment of the present specification. A cross-section of thepulmonary system comprising bronchus 91, normal alveolus 92, bullouslesion 93, and a bronchial neoplasm 94 is illustrated.

In one embodiment, the catheter 96 is inserted through the channel of abronchoscope 95 into the bronchus 91 and advanced into a bullous lesion93. The catheter 96 has two positioning elements, a conical positioningelement 97 and a disc shaped positioning element 98. The positioningelement 97 is conical having an insulated membrane covering. The conicalelement 97 positions the catheter 96 in the center of the bronchus 91and the insulated membrane prevents the escape of thermal energy orablative agent through the opening into the normal bronchus. The seconddisc shaped positioning element 98 is deployed in the bullous cavity 93positioning the catheter 96 in the middle of the bullous cavity 93. Anablative agent 9 is passed through the infusion port 99 for uniformdelivery into the sinus cavity. Predetermined length ‘l’ of the ablativesegment of the catheter 96 and diameter ‘d’ of the positioning element98 allow for estimation of the bullous cavity size and is used tocalculate the amount of thermal energy needed to ablate the diseasedbullous cavity 93. Optionally, the size of the cavity can be calculatedfrom radiological evaluation using a chest CAT scan or MRI. Optionaltemperature sensors are deployed close to the surface of the bullouscavity 93 to control the delivery of the ablative agent 9. In anembodiment, the ablative agent is steam which contracts on cooling. Thisfurther decreases the risk of leakage of the thermal energy into thenormal bronchus thus reducing any risk of thermal injury to adjacentnormal tissue.

In one embodiment, the positioning attachment must be separated from theablation region by a distance of greater than 0.1 mm, preferably 1 mmand more preferably 1 cm. In another embodiment, the positioningattachment can be in the ablated region as long as it does not cover asignificant surface area.

In one embodiment, there are preferably two positioning attachments. Inanother embodiment, the endoscope is used as one fixation point with onepositioning element. The positioning device is between 0.1 mm and 5 cm(preferably 1 mm to 2 cm). The distal positioning device is preferablycircular with a diameter between 0.1 mm and 10 cm, preferably 1 cm to 5cm.

In another embodiment for the ablation of a bronchial neoplasm 94, thecatheter 96 is inserted through the channel of a bronchoscope 95 intothe bronchus 91 and advanced across the bronchial neoplasm 94. Thepositioning element 98 is disc shaped having an insulated membranecovering. The positioning element 98 positions the catheter in thecenter of the bronchus 91 and the insulated membrane prevents the escapeof thermal energy or ablative agent through the opening into the normalbronchus. The ablative agent 9 is passed through the infusion port 99 ina non-circumferential pattern for uniform delivery of the ablative agentto the bronchial neoplasm 94. The predetermined length ‘l’ of theablative segment of the catheter and diameter ‘d’ of the positioningelement 98 are used to calculate the amount of thermal energy needed toablate the bronchial neoplasm 94.

The catheter could be advanced to the desired location of ablation usingendoscopic, laparoscopic, stereotactic or radiological guidance.Optionally the catheter could be advanced to the desired location usingmagnetic navigation.

In another embodiment, a positioning element is an inflatable balloon inthermal communication with the vapor delivery catheter. The balloon isinflated to a first volume which is used to measure the inner diameterof the bronchus. On delivery of ablative energy through the catheter, aportion of thermal energy is transferred to the air in the balloon whichfurther expands the balloon to a second volume which is up to 25%greater than the first volume and is ideally optimized to occlude thebronchus, preventing the leakage of ablative agent.

FIG. 9B illustrates bronchial ablation being performed by an ablationdevice 905 having an inflatable balloon 908 with at least one thermallyconducting element 919 attached thereto, in accordance with oneembodiment of the present specification. The ablation device 905 isinserted with its distal end positioned in a patient's bronchus 901proximate a bronchial wall 904 with a target tissue. The balloon 908 isinflated to a first volume to bring the thermally conducting element 919into contact with a bronchial wall 904. The ablative agent is thenreleased into the balloon 908, further expanding the volume of theballoon 908 and pushing the thermally conducting element 919 into thebronchial wall 904 and releasing the ablative energy into said wall 904,thus ablating structures in or around the wall 904. In variousembodiments, the thermally conducting element 919 comprises a solid orhollow needle. In various embodiments, a hollow needle includes a valvewhich is controlled by pressure, temperature, or both, and opens whenthe pressure or temperature in the vicinity of the valve exceeds apredefined threshold value.

Regarding pulmonary function, there are four lung volumes and four lungcapacities. A lung capacity consists of two or more lung volumes. Thelung volumes are tidal volume (VT), inspiratory reserve volume (IRV),expiratory reserve volume (ERV), and residual volume (RV). The four lungcapacities are total lung capacity (TLC), inspiratory capacity (IC),functional residual capacity (FRC), and vital capacity (VC). Measurementof the single-breath diffusing capacity for carbon monoxide (DLCO) is afast and safe tool in the evaluation of both restrictive and obstructivelung disease. Arterial blood gases (ABGs) are a helpful measurement inpulmonary function testing in selected patients. The primary role ofmeasuring ABGs in individuals that are healthy and stable is to confirmhypoventilation when it is suspected on the basis of medical history,such as respiratory muscle weakness or advanced COPD. Spirometryincludes tests of pulmonary mechanics such as measurements of forcedvital capacity (FVC), forced expiratory volume at the end of the firstsecond of forced expiration (FEV₁), forced expiratory flow (FEF) values,forced inspiratory flow rates (FIFs), and maximum voluntary ventilation(MVV). Measuring pulmonary mechanics assesses the ability of the lungsto move large volumes of air quickly through the airways to identifyairway obstruction.

In various embodiments, ablation therapy provided by the vapor ablationsystems of the present specification is delivered to achieve thefollowing therapeutic endpoints for pulmonary ablation: maintain atissue temperature at 100° C. or less; reduce TLC, defined as the volumein the lungs at maximal inflation, by at least 5% relative topre-treatment TLC; increase VT, defined as the volume of air moved intoor out of the lungs during quiet breathing, by at least 5% relative topre-treatment VT; decrease RV, defined as the volume of air remaining inthe lungs after a maximal exhalation, by 5% relative to pre-treatmentRV; increase ERV, defined as the maximal volume of air that can beexhaled from the end-expiratory position, by 5% relative topre-treatment ERV; increase IRV, defined as the maximal volume that canbe inhaled from the end-inspiratory level, by at least 5% relative topre-treatment IRV; increase IC by at least 5% relative to pre-treatmentIC; increase inspiratory vital capacity (IVC), defined as the maximumvolume of air inhaled from the point of maximum expiration, by at least5% relative to pre-treatment IVC; increase VC, defined as the volume ofair breathed out after the deepest inhalation, by at least 5% relativeto pre-treatment VC; decrease FRC, defined as the volume in the lungs atthe end expiratory position, by at least 5% relative to pre-treatmentFRC; decrease RV by at least 5% relative to pre-treatment RV; decreasealveolar gas volume (V^(A)) by at least 5% relative to pre-treatmentV^(A); no change in actual lung volume including the volume of theconducting airway (V^(L)) relative to pre-treatment V^(L); increase DLCOby at least 5% relative to pre-treatment DLCO; increase partial pressureof oxygen dissolved in plasma (PaO₂) by at least 2% and/or decreasepartial pressure of carbon dioxide dissolved in plasma (PaCO₂) by atleast 1% relative to pre-treatment PaO₂ and PaCO₂ levels; increase anyspirometry results by at least 5% relative to pre-treatment spirometryresults; increase FVC, defined as the vital capacity from a maximallyforced expiratory effort, by at least 5% relative to pre-treatment FVC;increase forced expiratory volume over time (FEV), defined as the volumeof air exhaled under forced conditions in the first t seconds, by atleast 5% relative to pre-treatment FEV; increase FEV₁ by at least 5%relative to pre-treatment FEV₁; increase FEF by at least 5% relative topre-treatment FEF; increase FEF′, defined as the maximum instantaneousflow achieved during a FVC maneuver, by at least 5% relative topre-treatment FEF^(max); increase FIF by at least 5% relative topre-treatment FIF; increase peak expiratory flow (PEF), defined as thehighest forced expiratory flow measured with a peak flow meter, by atleast 5% relative to pre-treatment PEF; increase MVV, defined as thevolume of air expired in a specified period during repetitive maximaleffort, by at least 5% relative to pre-treatment MVV.

FIG. 10A illustrates prostate ablation being performed on an enlargedprostrate in a male urinary system by using the device, in accordancewith an embodiment of the present specification. A cross-section of amale genitourinary tract having an enlarged prostate 1001, bladder 1002,and urethra 1003 is illustrated. The urethra 1003 is compressed by theenlarged prostate 1001. The ablation catheter 1005 is passed through thecystoscope 1004 positioned in the urethra 1003 distal to theobstruction. The positioning elements 1006 are deployed to center thecatheter in the urethra 1003 and one or more insulated needles 1007 arepassed to pierce the prostate 1001. The vapor ablative agent 1008 ispassed through the insulated needles 1007 thus causing ablation of thediseased prostatic tissue resulting in shrinkage of the prostate.

The size of the enlarged prostate could be calculated by using thedifferential between the extra-prostatic and intra-prostatic urethra.Normative values could be used as baseline. Additional ports forinfusion of a cooling fluid into the urethra can be provided to preventdamage to the urethra while the ablative energy is being delivered tothe prostrate for ablation, thus preventing complications such asstricture formation.

In one embodiment, the positioning attachment must be separated from theablation region by a distance of greater than 0.1 mm, preferably 1 mm to5 mm and no more than 2 cm. In another embodiment, the positioningattachment can be deployed in the bladder and pulled back into theurethral opening/neck of the bladder thus fixing the catheter. In oneembodiment, the positioning device is between 0.1 mm and 10 cm indiameter.

FIG. 10B is an illustration of transurethral prostate ablation beingperformed on an enlarged prostrate 1001 in a male urinary system usingan ablation device, in accordance with one embodiment of the presentspecification. Also depicted in FIG. 10B are the urinary bladder 1002and prostatic urethra 1003. An ablation catheter 1023 with a handle 1020and a positioning element 1028 is inserted into the urethra 1003 andadvanced into the bladder 1002. The position element 1028 is inflatedand pulled to the junction of the bladder with the urethra, thuspositioning needles 1007 at a predetermined distance from the junction.Using a pusher 1030, the needles 1007 are then pushed out at an anglebetween 30 and 90 degree from the catheter 1023 through the urethra 1003into the prostate 1001. Vapor is administered through a port 1038 thattravels through the shaft of the catheter 1023 and exits from openings1037 in the needles 1007 into the prostatic tissue, thus ablating theprostatic tissue. In one embodiment, the needles 1007 are insulated.Optional port 1039 allows for insertion of cool fluid at a temperature<37 degree C. through opening 1040 to cool the prostatic urethra.Optional temperature sensors 1041 can be installed to detect thetemperature of the prostatic urethra and modulate the delivery of vapor.

FIG. 10C is an illustration of transurethral prostate ablation beingperformed on an enlarged prostrate 1001 in a male urinary system usingan ablation device, in accordance with another embodiment of the presentspecification. Also depicted in FIG. 10B are the urinary bladder 1002and prostatic urethra 1003. An ablation catheter 1023 with a handle 1020and a positioning element 1048 is inserted into the urethra 1003 andadvanced into the bladder 1002. The positioning element 1048 is acompressible disc that is expanded in the bladder 1002 and pulled to thejunction of the bladder with the urethra, thus positioning needles 1007at a predetermined distance from the junction. Using a pusher 1030, theneedles 1007 are then pushed out at an angle between 30 and 90 degreefrom the catheter 1023 through the urethra 1003 into the prostate 1001.Vapor is administered through a port 1038 that travels through the shaftof the catheter 1023 and exits through openings 1037 in the needles 17into the prostatic tissue, thus ablating the prostatic tissue. In oneembodiment, the needles 1007 are insulated. Optional port 1039 allowsfor insertion of cool fluid at a temperature <37 degree C. throughopening 1040 to cool the prostatic urethra. Optional temperature sensors1041 can be installed to detect the temperature of the prostatic urethraand modulate the delivery of vapor.

FIG. 10D is a flow chart listing the steps involved in a transurethralenlarged prostate ablation process using an ablation catheter, inaccordance with one embodiment of the present specification. At step1012, an ablation catheter is inserted into the urethra and advanceduntil its distal end is in the bladder. A positioning element is thendeployed on the distal end of the catheter, at step 1014, and theproximal end of the catheter is pulled so that the positioning elementabuts the junction of the bladder with the urethra, thereby positioningthe catheter shaft within the urethra. A pusher at the proximal end ofthe catheter is actuated to deploy needles from the catheter shaftthrough the urethra and into the prostatic tissue at step 1016. At step1018, an ablative agent is delivered through the needles and into theprostate to ablate the target prostatic tissue.

FIG. 10E is an illustration of transrectal prostate ablation beingperformed on an enlarged prostrate in a male urinary system using anablation device, in accordance with one embodiment of the presentspecification. Also depicted in FIG. 10E are the urinary bladder 1002and prostatic urethra 1003. The ablation device comprises a catheter1023 with a needle tip 1024. An endoscope 1022 is inserted into therectum 1021 for the visualization of the enlarged prostate 1001. Invarious embodiments, the endoscope 1022 is an echoendoscope or atransrectal ultrasound such that the endoscope can be visualized usingradiographic techniques. The catheter 1023 with needle tip 1024 ispassed through a working channel of the endoscope and the needle tip1024 is passed transrectally into the prostate 1001. A close-upillustration of the distal end of the catheter 1023 and needle tip 1204is depicted in FIG. 10G. An ablative agent is then delivered through theneedle tip 1024 into the prostatic tissue for ablation. In oneembodiment, the catheter 1023 and needle tip 1024 are composed of athermally insulated material. In various embodiments, the needle tip1024 is an echotip or sonolucent tip that can be observed usingradiologic techniques for accurate localization in the prostate tissue.In one embodiment, an optional catheter (not shown) can be placed in theurethra to insert fluid to cool the prostatic urethra 1003. In oneembodiment, the inserted fluid has a temperature less than 37° C.

FIG. 10F is an illustration of transrectal prostate ablation beingperformed on an enlarged prostrate in a male urinary system using acoaxial ablation device having a positioning element, in accordance withanother embodiment of the present specification. Also depicted in FIG.10F are the urinary bladder 1002 and prostatic urethra 1003. Theablation device comprises a coaxial catheter 1023 having an internalcatheter with a needle tip 1024 and an external catheter with apositioning element 1028. An endoscope 1022 is inserted into the rectum1021 for the visualization of the enlarged prostate 1001. In variousembodiments, the endoscope 1022 is an echoendoscope or a transrectalultrasound such that the endoscope can be visualized using radiographictechniques. The coaxial catheter 1023 with needle tip 1024 andpositioning element 1028 is passed through a working channel of theendoscope such that the positioning element 1028 comes to rest upagainst the rectal wall and the internal catheter is advancedtransrectally, thereby positioning the needle tip 1024 at apredetermined depth in the prostate 1001. A close-up illustration of thedistal end of the catheter 1023 and needle tip 1204 is depicted in FIG.10G. In one embodiment, the positioning element is a compressible discthat has a first, compressed pre-employment configuration and a second,expanded deployed configuration once it has passed beyond the distal endof the endoscope 1022. An ablative agent is then delivered through theneedle tip 1024 into the prostatic tissue for ablation. In oneembodiment, the coaxial catheter 1023, needle tip 1024, and positioningelement 1028 are composed of a thermally insulated material. In variousembodiments, the needle tip 1024 is an echotip or sonolucent tip thatcan be observed using radiologic techniques for accurate localization inthe prostate tissue. In one embodiment, an optional catheter (not shown)can be placed in the urethra to insert fluid to cool the prostaticurethra 1003. In one embodiment, the inserted fluid has a temperatureless than 37° C.

FIG. 10H is a flow chart listing the steps involved in a transrectalenlarged prostate ablation process using an ablation catheter, inaccordance with one embodiment of the present specification. At step1042, an endoscope is inserted into the rectum of a patient forvisualization of the prostate. A catheter with a needle tip is thenadvanced, at step 1044, through a working channel of the endoscope andthrough the rectal wall and into the prostate. Radiologic methods areused to guide the needle into the target prostatic tissue at step 1046.At step 1048, an ablative agent is delivered through the needle and intothe prostate to ablate the target prostatic tissue.

In various embodiments, ablation therapy provided by the vapor ablationsystems of the present specification is delivered to achieve thefollowing therapeutic endpoints for prostate ablation: maintain a tissuetemperature at 100° C. or less; improve patient urine flow by at least5% relative to pre-treatment urine flow; decrease prostate volume by atleast 5% relative to pre-treatment prostate volume; ablate the prostatetissue without circumferentially ablating a urethral tissue; improveInternational Prostate Symptom Score (IPSS) by at least 5% relative to apre-treatment IPSS score, wherein the IPSS questionnaire, depicted inFIG. 10N, comprises a series of questions 1080 regarding a patient'surinary habits with numerical scores 1081 for each question; improveBenign Prostatic Hypertrophy Impact Index Questionnaire (BPHIIQ) scoreby at least 10% relative to a pre-treatment BPHIIQ score, wherein theBPHIIQ, depicted in FIG. 10O, comprises a series of questions 1085regarding a patient's urinary problems with numerical scores 1086 foreach question; and patient reported satisfaction with the ablationprocedure of greater than 25%.

FIG. 10I is an illustration of an ablation catheter 1050 for permanentimplantation in the body to deliver repeat ablation and FIG. 10J is atrocar 1056 used to place the ablation catheter 1050 in the body. FIG.10K is an illustration of the catheter 1050 of FIG. 10I and trocar 1056of FIG. 10J assembled for placement of the catheter 1050 into tissuetargeted for ablation in the human body. The catheter 1050 of FIG. 10Ihas an anchoring unit 1054, a shaft 1055 and a port 1057. The anchoringunit 1054 anchors the catheter 1050 in the tissue targeted for ablationand houses one or more openings 1059 for the exit of the ablative agent.Port 1057 resides in the subcutaneous tissue or at a site that is easilyaccessible for repeat ablation. An ablative agent is introduced into theport 1057 and travels through the shaft 1055 to the site for ablationand exits through the one or more openings 1059 in the anchoring unit1054. As illustrated in FIG. 10K, in the assembled configuration 1053,the trocar 1056 locks with the catheter 1050 and straightens theanchoring unit 1054 for easy placement of the catheter 1050.Alternatively, in one embodiment (not pictured), the anchoring unit is aballoon that is inflated to anchor the device in the desired tissue. Thesubcutaneous port 1057, in a manner similar to a subcutaneous port forchemotherapy, can be easily accessed using an insulated needle orcatheter for delivery of ablative agent for multiple repeat ablationsover time. The port 1057 obviates the need for repeat invasiveprocedures and the cost of catheter placement into the tissue forablation.

FIG. 10L is an illustration of pancreatic ablation being performed on apancreatic tumor 1065 in accordance with one embodiment of the presentspecification. The ablation device 1060 is similar to the devicedepicted in FIGS. 10E-10G and includes a needle 1061 configured to beinserted into a lesion to deliver vapor for ablation. The ablationdevice 1060 is passed through a channel of an echoendoscope 1063 whichhas been inserted into a gastrointestinal tract 1064 of a patient toview the patient's pancreas 1066. Vapor is delivered through the needle1061 of the ablation device 1060 to ablate the pancreatic tumor 1065.

FIG. 10M is a flowchart listing the steps involved in one embodiment ofa method of pancreatic ablation. At step 1070, an echoendoscope isadvanced proximate a pancreatic tissue. A pancreatic lesion to beablated is localized using the echoendoscope at step 1071. At step 1072,dimensions of the lesion are measured using the echoendoscope. One ofthe measured dimensions is used to calculate an amount of vapor todeliver at step 1073. The ablation needle is passed through a channel inthe echoendoscope and through a puncture in the gastrointestinal wallinto the pancreatic lesion at step 1074. At step 1075, suction isoptionally applied on the needle to aspirate fluid/cells from thelesion. Vapor is passed through the needle into the pancreatic lesion toheat the lesion while water is simultaneously circulated through anouter sheath of the needle to cool the puncture site at step 1076. Thearea of ablation is observed with the echoendoscope at step 1077. Thepassage of vapor is stopped once adequate ablation is achieved at step1078. At step 1079, the ablation needle is removed from theechoendoscope and the echoendoscope is removed from the patient.

FIG. 11 illustrates fibroid ablation being performed in a female uterusby using the ablation device, in accordance with an embodiment of thepresent specification. A cross-section of a female genitourinary tractcomprising a uterine fibroid 1111, uterus 1112, and cervix 1113 isillustrated. The ablation catheter 1115 is passed through thehysteroscope 1114 positioned in the uterus distal to the fibroid 1111.The ablation catheter 1115 has a puncturing tip 1120 that helps punctureinto the fibroid 1111. The positioning elements 1116 are deployed tocenter the catheter in the fibroid and insulated needles 1117 are passedto pierce the fibroid tissue 1111. The vapor ablative agent 1118 ispassed through the needles 1117 thus causing ablation of the uterinefibroid 1111 resulting in shrinkage of the fibroid.

FIG. 12A illustrates a blood vessel ablation 1240 being performed by anablation device, in accordance with one embodiment of the presentspecification. The ablation involves replacing the blood within thevessel with a conductive medium used to distribute and conduct anablative agent in the vessel. In one embodiment, the device used for theablation comprises a catheter 1220 with a distal end and a proximal end.The distal end of the catheter 1220 is provided with at least one port1222 used to remove blood from the vessel 1240, at least one other port1224 for injecting a conductive medium into the vessel 1240, and atleast one other port for delivering an ablative agent 1226 into thevessel 1240. In various embodiments, each port or any combination ofports is capable of removing blood, injecting a conductive medium,and/or delivering an ablative agent, as discussed with reference to theablation catheter of FIG. 2F. In one embodiment, the conductive mediumis water. In another embodiment, the conductive medium is saline. In oneembodiment, the ablative agent is steam. The proximal end of thecatheter 1220 is coupled to at least one source to provide suction, theconductive medium, and the ablative agent. In one embodiment, thecatheter 1220 further includes a sensor 1227 wherein measurementsprovided by said sensor are used to control the flow of the ablativeagent. In various embodiments, the sensor is configured to sense any oneor combination of blood flow and ablation parameter, including flow ofablative agent, temperature, and pressure.

In one embodiment, a first means for occluding blood flow is appliedproximally to the insertion point of the catheter into the blood vessel.In one embodiment, the first means comprises a tourniquet (not shown).In another embodiment, the first means comprises an intraluminalocclusive element 1228. In one embodiment, the intraluminal occlusiveelement 1228 includes a unidirectional valve 1229 to permit the flow ofblood into the ablation area and to restrict the flow of conductivemedium or ablative agent out of the ablation area. In one embodiment, asecond means for occluding blood flow is applied distally from theinsertion point of the catheter into the blood vessel. The second meansfor occluding blood flow acts to prevent blood flow back into theablation area and also prevents the passage of conductive medium andablative agent beyond the ablation area. In one embodiment, the secondmeans comprises a tourniquet. In another embodiment, the second meanscomprises a second intraluminal occlusive element. In one embodiment,the second intraluminal occlusive element includes a unidirectionalvalve to permit the flow of blood into the ablation area and to restrictthe flow of conductive medium or ablative agent out of the ablationarea.

FIG. 12B illustrates a blood vessel 1240 ablation being performed by anablation device, in accordance with another embodiment of the presentspecification. The ablation device is a coaxial catheter 1230 comprisingan internal catheter 1232 and an external catheter 1234. In oneembodiment, the internal catheter has a distal end with ports 1233 thatfunction in the same manner as those on the catheter of FIG. 12A and aproximal end coupled to a source in the same manner as the catheter ofFIG. 12A. The external catheter 1234 is composed of an insulatedmaterial and functions as an insulating sheath over the internalcatheter 1232. In the embodiment pictured in FIG. 12B, the deviceincludes at least one intraluminal occlusive device 1238 with aunidirectional valve 1239, coupled to the external catheter 1234 andpositioned proximally, with respect to blood flow, to the ablationdevice. The intraluminal occlusive device 1238 functions in the samemanner as that referenced with respect to FIG. 12A. In anotherembodiment, the intraluminal occlusive device is not coupled to theexternal catheter. In another embodiment, an additional intraluminaldevice is positioned distally from the ablation catheter. In variousother embodiments, the flow of blood is stopped by the application of atleast one tourniquet positioned proximally or distally from the ablationdevice, or a plurality of tourniquets positioned both proximally anddistally from the ablation device. In one embodiment, the internalcatheter 1232 further includes a sensor 1237 wherein measurementsprovided by said sensor are used to control the flow of the ablativeagent. In various embodiments, the sensor is configured to sense any oneor combination of blood flow and ablation parameter, including flow ofablative agent, temperature, and pressure.

FIG. 12C is a flow chart listing the steps involved in a blood vesselablation process using an ablation catheter, in accordance with oneembodiment of the present specification. At step 1202, a catheter isinserted into a patient and advanced to the target blood vessel. Theflow of blood into the target vessel is stopped at step 1204. Thecatheter tip is then inserted into the target vessel at step 1206. Atstep 1208, suction is applied to the catheter to remove blood from thetarget vessel. A conductive medium is then injected into the targetvessel through ports on the catheter at step 1210. Then, at step 1212,an ablative agent is delivered into the conductive medium to ablate thetarget vessel. Suction is applied to the catheter at step 1214 to removethe conductive medium and ablative agent.

In another embodiment, a coaxial balloon is used to ablate a bloodvessel. The coaxial balloon is made of an inner thermally permeableballoon which is air-tight and an outer thermally permeable balloon thatoptionally allows for passage of an ablative agent. The inner balloon isinflated with air until it comes into contact with the vessel wall. Theinflated inner balloon serves to displace the blood from the vesselwall. Using a pressure volume calculation, the inner dimensions of thevessel wall are calculated and these dimensions are used to calculatethe ablative energy needed. The ablative energy is then delivered into aspace between the inner and outer balloons. The passage of thermalenergy results in expansion of the inner balloon as previouslydescribed, further occluding the vessel wall while the ablative energypermeates through the wall of the outer balloon to ablate the vesselwall. On stoppage of the delivery of the ablative agent, the air in theinner balloon cools and the volume of the inner balloon is reduced tothe pre-treatment volume.

FIG. 12D illustrates a cardiac ablation catheter 1242 in accordance withone embodiment of the present specification and FIG. 12E illustratescardiac ablation being performed by the cardiac ablation catheter 1242of FIG. 12D. The cardiac ablation catheter 1242 can be used to ablatecardiac tissue to treat an arrhythmia, such as atrial fibrillation. Thecatheter 1242 includes an elongate inner shaft 1243 covered by an outershaft 1244. The inner shaft 1243 includes an inflatable balloon 1245proximal its distal end. A mapping catheter 1246 is attached to thedistal end of the inner shaft 1243 distal to the balloon 1245. Themapping catheter 1246 maps the area of cardiac tissue responsible forthe arrhythmia. The distal end of the outer shaft 1244 ends a distanceproximal to the balloon 1245 such that a portion of the inner shaft 1243between the balloon 1245 and outer shaft 1244 is exposed. Water 1247 canbe pumped through the outer shaft 1244 where it exits proximal to theballoon 1245 for cooling a space proximal to the balloon 1245. Water1247 can also be pumped through the inner shaft 1243 where it exitsdistal to the balloon 1245 and proximal to the mapping catheter 1246 forcooling a space distal to the balloon 1245. The balloon 1245 includes anablation or hot zone 1248 proximate its equator and a first cold zone inits top hemisphere 1249, cooled by water 1247 pumped through the innershaft 1243, and a second cold zone in its bottom hemisphere 1250, cooledby water 1247 pumped through the outer shaft 1244. The equatorial hotzone 1248 remains heated by vapor used to heat the inside of the balloon1245 and is distant enough from the water 1247 pumped through the innershaft 1243 and outer shaft 1244 such that it does not become cooled.Referring to FIG. 12E, the balloon 1245 of the catheter 1242 has beenpositioned in a heart 1251, proximate a pulmonary vein 1252. Heatsupplied to the balloon 1245 by vapor is transferred from the hot zone1248 to the target arrhythmia tissue 1253 to ablate the tissue 1253 andtreat the arrhythmia.

FIG. 12F is a flowchart illustrating the steps involved in oneembodiment of a method of using the catheter of FIG. 12D to ablatecardiac tissue. At step 1254, an arrhythmia area is mapped using themapping catheter. The balloon is inflated with air to a first pressure(P1) to cause the balloon to contact the target arrhythmia tissue atstep 1255. At step 1256, water is infused to cool the catheter andoptionally the top and bottom hemispheres of the balloon. In someembodiments, blood assists in cooling the top and bottom hemispheres ofthe balloon. At step 1257, steam is infused into the balloon to heat theinside of the balloon while simultaneously removing air from the balloonto maintain a second pressure (P2) equal to P1+/−25%. A hot zone on theballoon is created by the infused steam wherein the hot zone touches thecardiac tissue resulting in ablation at step 1258.

FIG. 12G illustrates a cardiac ablation catheter 1260 in accordance withanother embodiment of the present specification. The catheter 1260includes an elongate body 1261, a proximal end, and a distal end with anair/water lumen 1262 and a vapor lumen 1263 supplied by ports at itsproximal end. The air/water lumen 1262 is in fluid communication with amapping balloon 1264 attached to the distal end of the catheter 1260.The mapping balloon 1264 includes a plurality of mapping electrodes 1266within or attached to the outer surface of its walls. The mappingelectrodes 1266 map the area of cardiac tissue responsible for anarrhythmia. The vapor lumen 1263 is in fluid communication with anablation balloon 1265 attached to the distal end of the catheter 1260and positioned within the mapping balloon 1264. Once both balloons 1264,1265 are inflated, a length of the mapping balloon 1264 is greater thana length of the ablation balloon 1265 and a diameter of the ablationballoon 1265 approximates a diameter of the mapping balloon 1264. Duringuse, the mapping balloon 1264 is inflated with water or air and theablation balloon 1266 is inflated with vapor such that the ablationballoon 1265 comes into contact with the mapping balloon 1264 and themapping balloon 1264 comes into contact with the target cardiac tissueproximate the equators of both balloons 1264, 1265. This creates a hotzone or ablation zone 1267 proximate the equator of the mapping balloon1264. Cold zones 1271 are located on the mapping balloon 1264 where theinflated ablation balloon 1265 is not in contact with the inflatedmapping balloon 1264. Heat is transferred from inside the ablationballoon 1265 through the mapping balloon 1264 and into the cardiactissue to ablate the tissue and treat the arrhythmia.

FIG. 12H illustrates the mapping balloon 1264 with mapping electrodes1266 of the catheter 1260 of FIG. 12G. FIG. 12I illustrates a crosssectional view of a mid-shaft portion of the catheter 1260 of FIG. 12G.The catheter 1260 includes a compartmentalized outer wall 1268 whichincludes the air/water lumen 1262 and wires 1269 for the mappingelectrodes. The catheter 1260 also includes the vapor lumen 1263 and, inone embodiment, a guidewire lumen 1270. FIG. 12J illustrates a crosssectional view of a distal tip portion of the catheter 1260 of FIG. 12G.The catheter 1260 includes a plurality of mapping electrodes 1266 builtinto its outer wall or, in an embodiment, into the wall of the mappingballoon, the vapor lumen 1263, and a guidewire lumen 1270.

FIG. 12K is a flowchart illustrating the steps involved in oneembodiment of a method of using the catheter of FIG. 12G to ablatecardiac tissue. At step 1272, the mapping balloon is inflated to a firstpressure (P 1). An arrhythmia area is mapped using the mapping balloonat step 1273. At step 1274, the ablation balloon is inflated with vaporwith or without air to a second pressure (P2) greater than P1 to contactthe mapping balloon. At step 1275, a hot zone is created on the surfaceof the mapping balloon where the ablation balloon is touching themapping balloon and where the mapping balloon is touching the cardiactissue to ablate the cardiac tissue while cold zones exist where theablation balloon is not touching the mapping balloon. At step 1276,electrical activity is monitored during and after the ablation processto document complete ablation of the arrhythmia focus. Optionally, atstep 1277, the mapping electrodes monitor tissue impedance and tissuetemperature to guide the ablation.

In various embodiments, ablation therapy provided by the vapor ablationsystems of the present specification is delivered to achieve thefollowing therapeutic endpoints for cardiac ablation: maintain a tissuetemperature at 100° C. or less; ablate a cardiac tissue without damagingan esophageal tissue; at least 10% of patients revert to normal sinusrhythm for at least 1 week; at least 10% of patients remain in normalsinus rhythm for at least 1 week; decrease the number of atrialarrhythmia episodes by at least 5% relative to the number ofpre-treatment atrial arrhythmia episodes; decrease the number ofsupraventricular arrhythmia episodes by at least 5% relative to thenumber of pre-treatment supraventricular arrhythmia episodes; decreasethe number of ventricular arrhythmia episodes by at least 5% relative tothe number of pre-treatment ventricular arrhythmia episodes; and anincrease in esophageal temperature at any time during or post treatmentis less than 8° C. or an esophageal temperature at any time during orpost treatment is less than 45° C.

FIG. 13A illustrates a cyst ablation being performed by an ablationdevice, in accordance with one embodiment of the present specification.The device comprises an ablation catheter 1320 similar to thosedescribed with reference to FIGS. 2D-2F. The catheter 1320 is insertedinto the cyst 1340 and the contents of the cyst are removed via suctionthrough the ports 1333 at the distal end of the catheter 1320. Aconductive medium 1324 is then injected into the cyst 1340, followed bythe delivery of an ablative agent 1325 to ablate the cyst. In oneembodiment, the catheter 1320 includes a sensor 1328 whereinmeasurements provided by said sensor are used to control the flow of theablative agent. In one embodiment, the catheter includes echogenicelements to assist with the placement of the catheter into the cystunder ultrasonic guidance. In another embodiment, the catheter includesradio-opaque elements to assist with the placement of the catheter intothe cyst under radiologic guidance.

FIG. 13B illustrates an ablation device 1350 for cyst ablation or solidtumor ablation, in accordance with one embodiment of the presentspecification. The device 1350 includes a catheter 1351 attached to ahandle 1352. FIG. 13C illustrates the distal end of the catheter 1351 ofthe ablation device of FIG. 13B. FIG. 13D illustrates a needle 1353extending from the distal end of the catheter 1351 of the ablationdevice of FIG. 13B. FIG. 13E is a close-up illustration of the needle1353 extending from the distal end of the catheter 1351 of the ablationdevice of FIG. 13B.

FIG. 13F is a flow chart listing the steps involved in a cyst ablationprocess using an ablation catheter, in accordance with one embodiment ofthe present specification. At step 1302, a catheter is inserted into apatient and advanced to the target cyst. The catheter tip is theninserted into the target cyst at step 1304. At step 1306, suction isapplied to the catheter to remove at least a portion of the contents ofthe target cyst. A conductive medium is then injected into the targetcyst through ports on the catheter at step 1308. Then, at step 1310, anablative agent is delivered into the conductive medium to ablate thetarget cyst. Suction is applied to the catheter at step 1312 to removethe conductive medium and ablative agent.

FIG. 14 is a flow chart listing the steps involved in a solid tumorablation process using an ablation catheter, in accordance with oneembodiment of the present specification. At step 1402, a catheter isinserted into a patient and advanced to the target tumor. The cathetertip is then inserted into the target tumor at step 1404. A conductivemedium is injected into the target tumor through ports on the catheterat step 1406. Then, at step 1408, an ablative agent is delivered intothe conductive medium to ablate the target tumor. In one embodiment, thecatheter includes a sensor wherein measurements provided by said sensorare used to control the flow of the ablative agent. In one embodiment,the catheter includes echogenic elements to assist with the placement ofthe catheter into the tumor under ultrasonic guidance. In anotherembodiment, the catheter includes radio-opaque elements to assist withthe placement of the catheter into the tumor under radiologic guidance.

FIGS. 15A, 15B, and 15C illustrate a non-endoscopic device 1520 used forinternal hemorrhoid ablation, in accordance with one embodiment of thepresent specification. The device 1520 is inserted into the rectum of apatient to selectively ablate internal hemorrhoids. The device includesa blind, atraumatic and clear distal end 1526 for insertion into apatient's rectum. The device 1520 includes a piston 1521 that, whenpulled down, creates suction in a chamber or slot 1522 within the device1520. The suction draws a portion of rectal tissue with a hemorrhoidthrough an opening 1523 positioned along an outer surface of the device1520 and into the chamber 1522. A port 1524 on the proximal end of thedevice 1520 is used to provide an ablative agent 1525 to the chamber1522 to ablate the hemorrhoid. In one embodiment, the device is composedof a thermally insulated material to avoid the transfer of ablativeenergy to the surrounding rectal mucosa. In one embodiment, the ablativeagent is steam. Referring to FIG. 15B, in one embodiment, the device1520 includes a viewing port 1528 through which an operator can observecapturing of the target tissue to ensure proper hemorrhoid ablation. Inone embodiment, the device 1520 further includes at least oneillumination source 1527 for illuminating the rectal tissue andhemorrhoid to assist the operator with locating the target tissue.Referring to FIG. 15C, in one embodiment, the device 1520 furtherincludes a track 1529 configured to circulate ablative agent 1525 aboutthe target tissue that has been captured through opening 1523.

FIG. 15D is a flow chart listing the steps involved in an internalhemorrhoid ablation process using a non-endoscopic ablation device, inaccordance with one embodiment of the present specification. At step1502, the device described with reference to FIGS. 15A, 15B, and 15C isinserted into the rectum of a patient with internal hemorrhoids. Apiston on the device is actuated to create suction and draw a portion ofhemorrhoid tissue into a slot in the device at step 1504. Then, at step1506, an ablative agent is delivered into the slot via a port on thedevice to ablate the hemorrhoid. The piston is released at step 1508 toremove suction, thereby releasing the portion of rectal tissue.

FIG. 15E illustrates a non-endoscopic device 1530 used for internalhemorrhoid ablation, in accordance with another embodiment of thepresent specification. The device 1530 includes a device body 1538having a proximal end, a distal end, and a lumen within. The deviceincludes a blind, atraumatic and clear distal end 1531 for insertioninto a patient's rectum. An articulating arm 1533 is coupled to a handle1539 on the device body 1538 about a pivot point 1541. A compressioncomponent 1540 is attached to the articulating arm 1533 and ispositioned and movable within the proximal end of the device body 1538.The device 1530 is inserted into a rectum of a patient and includes anopening, chamber, or slot 1532 positioned along an outer surface of thedevice body 1538 for receiving a portion of rectal tissue with ahemorrhoid. Rotating the articulating arm 1533 relative to the handle1539 in a first direction causes the compression component 1540 to movein a proximal direction within the proximal end of the device body 1538,creating suction and drawing the received rectal tissue and hemorrhoidinto the opening 1532. The articulating arm 1533 is rotated in a seconddirection opposite said first direction to move the compressioncomponent 1540 in a distal direction within the proximal end of thedevice body 1538, compressing the captured hemorrhoid within the opening1532 to reduce a cross-sectional area of the hemorrhoid. The compressioncomponent 1540 includes a one-way valve 1534 to allow for air within theopening 1532 to escape during compression. An ablative agent 1536 isintroduced via an inlet tube 1535 attached to the compression component1540 to ablate the hemorrhoid captured in the opening 1532. In oneembodiment, the ablative agent is steam. In one embodiment, the device1530 further includes at least one illumination source 1537 forilluminating the rectal tissue and hemorrhoid to assist the operatorwith locating the target tissue.

FIG. 15F is a flowchart listing the steps of a method for ablating aninternal hemorrhoid using the device of FIG. 15E, in accordance with oneembodiment of the present specification. At step 1550, the device isinserted into a patient's rectum to visualize the rectal tissue andhemorrhoid. In one embodiment, an optional illumination source isilluminated to assist with visualization of the target tissue at step1551. The target tissue is engaged with the opening in the device atstep 1552. At step 1553, the articulating arm is rotated in a firstdirection to create suction and draw the engaged target tissue furtherinto the opening. Then, at step 1554, the articulating arm is rotated ina second direction opposite said first direction to compress the targettissue within the opening, thereby reducing the cross-sectional area ofthe target tissue. Ablative agent is applied to the compressed targettissue at step 1555 until the desired therapeutic effect is achieved.Compression of the target tissue is released at step 1556 and suction ofthe target tissue is then released at step 1557. The target tissue isthen disengaged from the device at step 1558.

FIG. 15G illustrates a non-endoscopic device 1560 used for internalhemorrhoid ablation, in accordance with yet another embodiment of thepresent specification. The device 1560 includes an insertion member 1561having an elongate cylindrical body, a proximal end, and a distal end. Aclear tubular member 1562 is attached to the distal end of the insertionmember 1561. The clear tubular member 1562 functions to capture thehemorrhoid (target tissue) and allows the operator to visualize thehemorrhoid within. The proximal end of the insertion member 1561 isattached to a handle 1563. The handle 1563 includes a switch control1564 for controlling suction on the device 1560 and a suction inlet 1565for connection to a suction source. The insertion member 1561 includes asuction lumen extending along its length and in fluid communication witha similar suction lumen within the handle 1563. The suction lumen in thehandle 1563 is in fluid communication with the suction inlet 1565. Thesuction lumen in the insertion member 1561 is positioned in the centerof the insertion member 1561 and ends in a suction port 1566, asdepicted in the cross section view of the distal end of the insertionmember 1561 shown in FIG. 15G. Suction provided at the suction inlet1565 is transferred to the suction port 1566, where said suction drawsthe target tissue into the tubular member 1562.

A catheter 1567 having a proximal end and a distal end is attached viaits distal end to the proximal end of the insertion member 1561 andincludes a vapor inlet 1568 at its proximal end. The insertion member1561 includes at least one vapor lumen extending along its length and influid communication with the catheter 1567. In one embodiment, the vaporlumen splits into four separate vapor lumens positioned about theperiphery of the insertion member 1561 which all end in vapor ports1569, as depicted in the cross section view of the distal end of theinsertion member 1561 shown in FIG. 15G. Vapor provided at the vaporinlet 1568 is transferred to the vapor ports 1569, where said vaporablates the target tissue captured in the tubular member 1562. In oneembodiment, as depicted in the cross section view of the distal end ofthe insertion member 1561, the clear tubular member 1562 includes a heatsensitive compression mechanism 1570 which is open at room temperatureand compresses the engaged hemorrhoid at a temperature higher than thebody temperature. In one embodiment, the compression mechanism 1570 iscomposed of a shape memory alloy (SMA). In one embodiment, the SMA isNitinol. In one embodiment, the austenite finish (Af) temperature, ortemperature at which the transformation from martensite to austenitefinishes on heating (alloy undergoes a shape change to become acompressed mechanism 1570), of the SMA is greater than 37° C. In otherembodiments, the Af temperature of the SMA is greater than 50° C. butless than 100° C.

FIG. 15H is a flowchart listing the steps of a method for ablating aninternal hemorrhoid using the device of FIG. 15G, in accordance with oneembodiment of the present specification. At step 1575, the insertionmember of the device is inserted into a patient's rectum proximate atarget tissue. The device is manipulated to engage the target tissuewith the tubular member at step 1576. At step 1577, the switch controlis activated to provide suction and draw the target tissue into thetubular member. Then, at step 1578, vapor is delivered through the vaporports to ablate the target tissue captured in the tubular member. Oncethe desired level of treatment has been achieved, the switch control isactivated to remove the suction and release the target tissue from thetubular member at step 1579. The target tissue is disengaged from thetubular member and the insertion member is removed from the patient atstep 1580.

FIG. 16A illustrates an endoscopic device 1620 used for internalhemorrhoid ablation, in accordance with one embodiment of the presentspecification. In one embodiment, the device 1620 is composed of athermally insulated, transparent material. The device 1620 is mounted tothe distal end of an endoscope 1630 and both are inserted into thepatient's rectum. Suction is applied to the endoscope 1630, drawing aportion of rectal tissue with a hemorrhoid into a chamber or slot 1622in the device 1620.

In one embodiment, an ablative agent 1625 is delivered to the chamber orslot 1622 through a port 1624 in the device 1620. In another embodiment,a needle (not shown) is advanced through the port 1624 and inserted intothe rectal submucosa at the position of the hemorrhoid. An ablativeagent is then injected directly into the hemorrhoid through the needlefor selective hemorrhoid ablation.

FIG. 16B is a flow chart listing the steps involved in an internalhemorrhoid ablation process using an endoscopic ablation device, inaccordance with one embodiment of the present specification. At step1602, an endoscope with an ablation device coupled to its distal end isinserted into the rectum of a patient with internal hemorrhoids. At step1604, suction is applied to the endoscope to draw a portion of rectaltissue with a hemorrhoid into a chamber in the device.

In one embodiment, at step 1606, an ablative agent is delivered througha port on the device into the chamber to ablate the hemorrhoid. Suctionis then removed from the endoscope at step 1608 to release the portionof rectal tissue.

In another embodiment, at step 1610, a needle is advanced through theport on the device, through the chamber, and into the hemorrhoid. Anablative agent is then injected at step 1612 through the needle into thehemorrhoid to ablate said hemorrhoid. At step 1614, the needle isremoved from the hemorrhoid. Suction is then removed from the endoscopeat step 1616 to release the portion of rectal tissue.

In another embodiment, compressive force is applied to the engagedhemorrhoid to reduce the cross-sectional area of the hemorrhoid prior toapplying the thermal ablation, improving the efficacy of thermalablation. In one embodiment, compressive force is applied by a heatsensitive compression mechanism which is uncompressed at roomtemperature and compresses the engaged hemorrhoid at a temperaturehigher than the body temperature. In one embodiment, the compressionmechanism is composed of a shape memory alloy (SMA). In one embodiment,the SMA is Nitinol. In one embodiment, the Af temperature of the SMA isgreater than 37° C. In other embodiments, the Af temperature of the SMAis greater than 50° C. but less than 100° C.

FIG. 17A illustrates a stent 1720 used to provide localized ablation toa target tissue, in accordance with one embodiment of the presentspecification. Similar to conventional stents, the ablation stent 1720of the present specification has a compressed, pre-deploymentconfiguration and an expanded, post-deployment configuration. Thepre-deployment configuration assists with delivery of the stent and thepost-deployment configuration helps to keep the stent positionedcorrectly. The stent 1720 is covered with a semi-permeable or conductivemembrane 1722 that conducts an ablative agent or ablative energy fromwithin the stent lumen to the external surface of the stent in asufficient amount, resulting in ablation of the tissue in contact withthe stent 1720. The membrane allows for the transfer of ablative energyfrom inside the stent to the surrounding tissue while preventing leakageof a significant amount of fluid from inside the stent to thesurrounding tissue. In various embodiments, the membrane 1722 includesat least one opening or movable flap of membrane material 1723 for thetransfer of an ablative agent 1724 from the stent lumen to thesurrounding tissue. In some embodiments, the flaps 1723 comprise aplurality of individual overlapping membranes attached to the stent 1720with intervening unattached areas. The flaps 1723 can be moved in adirection away from the stent 1720 by force of the ablative agent 1724pushing against the membrane 1722, allowing the ablative agent 1724 toescape from the stent lumen into the surrounding tissues. The unattachedportions of the flaps 1723 act as unidirectional flap valves (similar toa drape), allowing for ablative agent 1724 to exit the stent lumen butpreventing the ingrowth of tumor or tissue into the stent 1720. Afterthe ablative agent 1724 has exited the stent 1720, the flaps 1723 layback against the stent 1720 and block the ablative agent 1724 fromre-entering the stent 1724 or tissue in-growth into the stent. In oneembodiment, the stent 1720 is composed of a wire mesh. In oneembodiment, the membrane 1722 is composed of a thermally conductivematerial. In one embodiment, the membrane is composed of silicone.Optionally, in some embodiments, the silicone membrane includes poreswhich allow for the transmission of the ablative agent without allowingfor substantial ingrowth of tumor tissue. The pores could optionally beexpandable and have a greater dimension when the ablative agent isapplied to allow for passage of ablative agent or energy while thedimension shrinks to a smaller dimension during non-therapy times toprevent tumor ingrowth. In other embodiments, the membrane is composedof polytetrafluoroethylene (PTFE), perfluoroelastomer (PFE), fluorinatedethylene propylene (FEP) or any other suitable material known in thefield.

FIG. 17B illustrates a catheter 1730 used to deploy, and provide anablative agent to, the stent of FIG. 17A. The catheter 1730 has aproximal end and a distal end with a shaft 1731 having a lumentherebetween. In one embodiment, the catheter 1730 is composed of athermally insulated material. The ablative agent 1733 enters the lumenof the catheter from the proximal end 1732. The catheter 1730 has one ormore openings 1735 at the distal end that allow for the ablative agent1733 to exit the catheter shaft 1731 and enter the stent lumen. Invarious embodiments, the catheter shaft 1731 has one or more positioningelements 1734 to position the at least one opening 1735 at a desiredlocation inside the stent lumen. These positioning elements 1734 alsoact as occlusive elements to prevent the passage of ablative agent intothe adjacent normal tissue. In one embodiment, the positioning elementshave a smaller first volume for positioning and a higher second volumefor occlusion. The increase in volume from said first volume to saidsecond volume is triggered by passage of the ablative agent whereinthermal energy of the ablative agent heats the air in the positioningelement to the second volume, resulting in a better seal while theablative agent is being delivered. The transfer of thermal energy to theair in the balloon occurs along the length of the catheter. Ondiscontinuation of the thermal energy delivery, the air inside theballoon cools and the balloon volume gradually decreases from theocclusive second volume to the positioning first volume. In someembodiments, this increase in volume is undesirable and a balloon madeof a non-compliant material that does not expand is used. In variousembodiments, optional lumens are available for the passage of aguidewire or injection of radiologic contrast material.

FIG. 17C illustrates the stent 1720 of FIG. 17A working in conjunctionwith the catheter 1730 of FIG. 17B. Ablative agent 1733 is provided tothe proximal end 1732 of the catheter 1730 and travels through thecatheter shaft 1731 to the distal end of the catheter 1730. The ablativeagent 1733 exits the catheter 1730 through the openings 1735 at thedistal end of the catheter 1730. The ablative agent 1733 is transferredto the surrounding tissues via the conductive membrane on the stent1720. The positioning elements 1734 prevent the escape of ablative agent1733 from the proximal and distal ends of the stent 1720.

FIG. 17D illustrates the stent of FIG. 17A and the catheter of FIG. 17Bpositioned in a bile duct 1741 obstructed by a pancreatic tumor 1740. Astent 1720 is placed in the bile duct to open the obstruction. The stent1720 has a thermally conducting membrane 1722 that allows for transferof ablative energy from inside the stent lumen to the surroundingtissue. In one embodiment, the membrane 1722 has openings to allow forthe passage of the ablative agents from inside the stent lumen to thesurrounding tissue. The catheter 1730 is used to deliver the catheter atinitial deployment and to deliver ablative agent. The catheter 1730 isalso used for subsequent ablation in an already deployed stent 1720. Theablative agent 1733 is delivered to the lumen of the stent through atleast one opening 1735 in the catheter shaft. The ablative agent thendelivers the ablative energy from the ablative agent 1733 through thethermally conducting membrane 1724 or allows for passage of the ablativeagent 1733 through the openings into the surrounding tissue to ablatethe tumor 1740. The catheter has a first positioning element 1734 at thedistal end to position the catheter at a fixed distance from the distalend of the stent 1720. This positioning element is also used anocclusive member to prevent the flow of the ablative agent 1733 outsidethe lumen of the stent into the normal healthy tissue of the bile duct1741. In one embodiment, the catheter has a second positioning element1735 at the proximal end of the stent serving similar function as thefirst positioning element 1734. In another embodiment, a bare metalstent is used and the ablative energy is passed through the intersticesof the stent.

In various embodiments, ablation therapy provided by the vapor ablationsystems of the present specification is delivered to achieve thefollowing therapeutic endpoints for a tumor in or proximate the bileduct: maintain a tissue temperature of 100° C. or less; ablate at least50% of the surface area of a targeted cancer mucosa to a sufficientdepth such that after ablation a cross-sectional area improves by atleast 10% relative to a pre-treatment cross-sectional area; biliary flowimproves by at least 10% relative to pre-treatment biliary flow; tumorvolume decreases by at least 10% relative to a pre-treatment tumorvolume.

FIG. 17E is a flow chart listing the steps involved in a hollow tissueor organ ablation process using an ablation stent and catheter, inaccordance with one embodiment of the present specification. At step1702, the catheter with the ablation stent coupled to its distal end isinserted into a hollow tissue of a patient. The catheter is thenadvanced at step 1704 to the target lesion and the stent is deployed. Atstep 1706, ablative agent is delivered to the stent lumen via ports onthe catheter. The ablative agent or energy is then conducted to thesurrounding tissue via the conductive membrane on the stent. Onceablation is completed, the catheter is removed from the patient at step1708. If further ablation is needed, the catheter is re-inserted at step1710 and advanced to the location of the stent. Ablation is thenre-performed at step 1706. The deployment of the stent and delivery ofablative energy can be performed in separate steps and at separatetimes. For example, the ablation can be performed at a future time afterthe placement of the stent to shrink the growth of an expanding tumor.Multiple serial ablations can be performed through the same stent overtime.

FIG. 18 illustrates a vapor delivery system using an RF heater forsupplying vapor to the ablation device, in accordance with an embodimentof the present specification. In an embodiment, the vapor is used as anablative agent in conjunction with the ablation device described in thepresent specification. RF heater 1864 is located proximate a pressurevessel 1842 containing a liquid 1844. RF heater 1864 heats vessel 1842,in turn heating the liquid 1844. The liquid 1844 heats up and begins toevaporate causing an increase in pressure inside the vessel 1842. Thepressure inside vessel 1842 can be kept fairly constant by providing athermal switch 1846 that controls resistive heater 1864. Once thetemperature of the liquid 1844 reaches a predetermined temperature, thethermal switch 1846 shuts off RF heater 1864. The vapor created inpressure vessel 1842 may be released via a control valve 1850. As thevapor exits vessel 1842, a pressure drop is created in the vesselresulting in a reduction in temperature. The reduction of temperature ismeasured by thermal switch 1846, and RF heater 1864 is turned back on toheat liquid 1844. In one embodiment, the target temperature of vessel1842 may be set to approximately 108° C., providing a continuous supplyof vapor. As the vapor is released, it undergoes a pressure drop, whichreduces the temperature of the vapor to a range of approximately 90-100°C. As liquid 1844 in vessel 1842 evaporates and the vapor exits vessel1842, the amount of liquid 1844 slowly diminishes. The vessel 1842 isoptionally connected to reservoir 1843 containing liquid 1844 via a pump1849 which can be turned on by the controller 1824 upon sensing a fallin pressure or temperature in vessel 1842, delivering additional liquid1844 to the vessel 1842.

Vapor delivery catheter 1816 is connected to vessel 1842 via a fluidconnector 1856. When control valve 1850 is open, vessel 1842 is in fluidcommunication with delivery catheter 1816 via connector 1856. Controlswitch 1860 may serve to turn vapor delivery on and off via actuator1848. For example, control switch 1860 may physically open and close thevalve 1850, via actuator 1848, to control delivery of vapor stream fromthe vessel 1842. Switch 1860 may be configured to control otherattributes of the vapor such as direction, flow, pressure, volume, spraydiameter, or other parameters.

Instead of, or in addition to, physically controlling attributes of thevapor, switch 1860 may electrically communicate with a controller 1824.Controller 1824 controls the RF heater 1864, which in turn controlsattributes of the vapor, in response to actuation of switch 1860 by theoperator. In addition, controller 1824 may control valves temperature orpressure regulators associated with catheter 1816 or vessel 1842. A flowmeter 1852 may be used to measure the flow, pressure, or volume of vapordelivery via the catheter 1816. The controller 1824 controls thetemperature and pressure in the vessel 1842 and the time, rate, flow,and volume of vapor flow through the control valve 1850. Theseparameters are set by the operator 1811. The pressure created in vessel1842, using the target temperature of 108° C., may be in the order of 25pounds per square inch (psi) (1.72 bars).

FIG. 19 illustrates a vapor delivery system using a resistive heater forsupplying vapor to the ablation device, in accordance with an embodimentof the present specification. In an embodiment, the generated vapor isused as an ablative agent in conjunction with the ablation devicedescribed in the present specification. Resistive heater 1940 is locatedproximate a pressure vessel 1942. Vessel 1942 contains a liquid 1944.Resistive heater 1940 heats vessel 1942, in turn heating liquid 1944.Accordingly, liquid 1944 heats and begins to evaporate. As liquid 1944begins to evaporate, the vapor inside vessel 1942 causes an increase inpressure in the vessel. The pressure in vessel 1942 can be kept fairlyconstant by providing a thermal switch 1946 that controls resistiveheater 1940. When the temperature of liquid 1944 reaches a predeterminedtemperature, thermal switch 1946 shuts off resistive heater 1940. Thevapor created in pressure vessel 1942 may be released via a controlvalve 1950. As the vapor exits vessel 1942, vessel 1942 experiences apressure drop. The pressure drop of vessel 1942 results in a reductionof temperature. The reduction of temperature is measured by thermalswitch 1946, and resistive heater 1940 is turned back on to heat liquid1944. In one embodiment, the target temperature of vessel 1942 may beset to approximately 108° C., providing a continuous supply of vapor. Asthe vapor is released, it undergoes a pressure drop, which reduces thetemperature of the vapor to a range of approximately 90-100° C. Asliquid 1944 in vessel 1942 evaporates and the vapor exits vessel 1942,the amount of liquid 1944 slowly diminishes. The vessel 1942 isconnected to another vessel 1943 containing liquid 1944 via a pump 1949which can be turned on by the controller 1924 upon sensing a fall inpressure or temperature in vessel 1942 delivering additional liquid 1944to the vessel 1942.

Vapor delivery catheter 1916 is connected to vessel 1942 via a fluidconnector 1956. When control valve 1950 is open, vessel 1942 is in fluidcommunication with delivery catheter 1916 via connector 1956. Controlswitch 1960 may serve to turn vapor delivery on and off via actuator1948. For example, control switch 1960 may physically open and close thevalve 1950, via actuator 1948, to control delivery of vapor stream fromthe vessel 1942. Switch 1960 may be configured to control otherattributes of the vapor such as direction, flow, pressure, volume, spraydiameter, or other parameters. Instead of, or in addition to, physicallycontrolling attributes of the vapor, switch 1960 may electricallycommunicate with a controller 1924. Controller 1924 controls theresistive heater 1940, which in turn controls attributes of the vapor,in response to actuation of switch 1960 by the operator. In addition,controller 1924 may control valves temperature or pressure regulatorsassociated with catheter 1916 or vessel 1942. A flow meter 1952 may beused to measure the flow, pressure, or volume of vapor delivery via thecatheter 1916. The controller 1924 controls the temperature and pressurein the vessel 1942 as well as time, rate, flow, and volume of vapor flowthrough the control valve 1950. These parameters are set by the operator1911. The pressure created in vessel 1942, using the target temperatureof 108° C., may be on the order of 25 pounds per square inch (psi) (1.72bars).

FIG. 20 illustrates a vapor delivery system using a heating coil forsupplying vapor to the ablation device, in accordance with an embodimentof the present specification. In an embodiment, the generated vapor isused as an ablative agent in conjunction with the ablation devicedescribed in the present specification. The vapor delivery systemincludes a conventional generator 2000 that is commonly used inoperating rooms to provide power to specialized tools, i.e., cutters.The generator 2000 is modified to include an integrated liquid reservoir2001. In one embodiment, the reservoir 2001 is filled with roomtemperature pure water. The reservoir 2001 portion of the generator 2000is connected to the heating component 2005 via a reusable active cord2003. In one embodiment, the reusable active cord 2003 may be used up to200 times. The cord 2003 is fixedly attached via connections at bothends to withstand operational pressures, and preferably a maximumpressure, such that the cord does not become disconnected. In oneembodiment, the connections can resist at least 1 atm of pressure. Inone embodiment, the connections are of a luer lock type. The cord 2003has a lumen through which liquid flows to the heating component 2005. Inone embodiment, the heating component 2005 contains a coiled length oftubing 2006. As liquid flows through the coiled tubing 2006, it isheated by the surrounding heating component 2005 in a fashion similar toa conventional heat exchanger. As the liquid is heated, it becomesvaporized. The heating component contains a connector 2007 thataccommodates the outlet of vapor from the coiled tubing 2006. One end ofa single use cord 2008 attaches to the heating component 2005 at theconnector 2007. The connector 2007 is designed to withstand pressuresgenerated by the vapor inside the coiled tubing 2006 during operation.In one embodiment, the connector 2007 is of a luer lock type. Anablation device 2009 is attached to the other end of the single use cord2008 via a connection able to withstand the pressures generated by thesystem. In one embodiment, the ablation device is integrated with acatheter. In another embodiment, the ablation device is integrated witha probe. The single use cord 2008 has a specific luminal diameter and isof a specific length to ensure that the contained vapor does notcondense into liquid while simultaneously providing the user enoughslack to operate. In addition, the single use cord 2008 providessufficient insulation so that personnel will not suffer burns whencoming into contact with the cord. In one embodiment, the single usecord has a luminal diameter of less than 3 mm, preferably less than 2.6mm, and is longer than 1 meter in length.

In one embodiment, the system includes a foot pedal 2002 by which theuser can supply more vapor to the ablation device. Depressing the footpedal 2002 allows liquid to flow from the reservoir 2001 into theheating component 2005 where it changes into vapor within the coiledtubing 2006. The vapor then flows to the ablation device via the singleuse tube 2008. The ablation device includes an actuator by which theuser can open small ports on the device, releasing the vapor andablating the target tissue.

FIG. 21 illustrates the heating component 2105 and coiled tubing 2106 ofthe heating coil vapor delivery system of FIG. 20, in accordance with anembodiment of the present specification. Liquid arrives through areusable active cord (not shown) at a connection 2102 on one side of theheating component 2105. The liquid then travels through the coiledtubing 2106 within the heating component 2105. The coiled tubing iscomposed of a material and configured specifically to provide optimalheat transfer to the liquid. In one embodiment, the coiled tubing 2106is copper. The temperature of the heating component 2105 is set to arange so that the liquid is converted to vapor as it passes through thecoiled tubing 2106. In one embodiment, the temperature of the heatingcomponent 2105 can be set by the user through the use of a temperaturesetting dial 2108. In one embodiment, the heating component contains anon/off switch 2109 and is powered through the use of an attached ACpower cord 2103. In another embodiment, the heating component receivespower through an electrical connection integrated into and/orfacilitated by the active cord connection to the reservoir. The vaporpasses through the end of the coiled tubing 2106 and out of the heatingcomponent 2105 through a connector 2107. In one embodiment, theconnector 2107 is located on the opposite side of the heating component2105 from the inlet connection 2102. A single use cord (not shown)attaches to the connector 2107 and supplies vapor to the ablationdevice.

FIG. 22A illustrates the unassembled interface connection between theablation device 2208 and the single use cord 2201 of the heating coilvapor delivery system of FIG. 20, in accordance with an embodiment ofthe present specification. In this embodiment, the ablation device 2208and single use cord 2201 are connected via a male-to-male double luerlock adapter 2205. The end of the single use cord 2201 is threaded toform a female end 2202 of a luer lock interface and connects to one endof the adapter 2205. The ablation device 2208 includes a smallprotrusion at its non-operational end which is also threaded to form afemale end 2207 of a luer lock interface and connects to the other endof the adapter 2205. The threading luer lock interface provides a secureconnection and is able to withstand the pressures generated by theheating coil vapor delivery system without becoming disconnected.

FIG. 22B illustrates the assembled interface connection between theablation device 2208 and the single use cord 2201 of the heating coilvapor delivery system of FIG. 20, in accordance with an embodiment ofthe present specification. The male-to-male double luer lock adapter2205 is pictured securing the two components together. The double luerlock interface provides a stable seal, allows interchangeability betweenablation devices, and enables users to quickly replace single use cords.

FIG. 23 illustrates a vapor ablation system using a heater or heatexchange unit for supplying vapor to the ablation device, in accordancewith another embodiment of the present specification. In the picturedembodiment, water for conversion to vapor is supplied in a disposable,single use sterile fluid container 2305. The container 2305 is sealedwith a sterile screw top 2310 that is punctured by a needle connector2315 provided on a first end of a first filter member 2320. The secondend of the first filter member 2320, opposite the first end, isconnected to a pump 2325 for drawing the water from the fluid container2305, through the first filter member 2320, and into the heater or heatexchange unit 2330. The system includes a microcontroller ormicroprocessor 2335 for controlling the actions of the pump 2325 andheater or heat exchange unit 2330. The heater or heat exchange unit 2330converts the water into vapor (steam). The increase in pressuregenerated during the heating step drives the vapor through an optionalsecond filter member 2340 and into the ablation catheter 2350. In oneembodiment, the heater or heat exchange unit 2330 includes a one-wayvalve at its proximal end to prevent the passage of vapor back towardthe pump 2325. In various embodiments, optional sensors 2345 positionedproximate the distal end of the catheter 2350 measure one or more oftemperature, pressure, or flow of vapor and transmit the information tothe microcontroller 2335, which in turn controls the rate of the pump2325 and the level of vaporizing energy provided by the heater or heatexchange unit 2330.

FIG. 24 illustrates the fluid container 2405, first filter member 2420,and pump 2425 of the vapor ablation system of FIG. 23. As can be seen inthe pictured embodiment, the system includes a water-filled, disposable,single use sterile fluid container 2405 and a pump 2425 with a firstfilter member 2420 disposed therebetween. The first filter member 2420is connected to the container 2405 and pump 2425 by two first and secondlengths of sterile tubing 2407, 2422 respectively, and includes a filterfor purifying the water used in the ablation system.

FIGS. 25 and 26 illustrate first and second views respectively, of thefluid container 2505, 2605, first filter member 2520, 2620, pump 2525,2625, heater or heat exchange unit 2530, 2630, and microcontroller 2535,2635 of the vapor ablation system of FIG. 23. The container 2505, 2605is connected to the first filter member 2520, 2620 by a first length ofsterile tubing 2507, 2607 and the first filter member 2520, 2620 isconnected to the pump 2525, 2625 by a second length of sterile tubing2522, 2622. A third length of sterile tubing 2527, 2627 connects thepump 2525, 2625 to the heater or heat exchange unit 2530, 2630. Themicrocontroller 2535, 2635, is operably connected to the pump 2525, 2625by a first set of control wires 2528, 2628 and to the heater or heatexchange unit 2530, 2630 by a second set of control wires 2529, 2629.The arrows 2501, 2601 depict the direction of the flow of water from thecontainer 2505, 2605, through the first filter member 2520, 2620 andpump 2525, 2625 and into the heater or heat exchange member 2530, 2630where it is converted to vapor. Arrow 2531, 2631 depicts the directionof flow of vapor from the heater or heat exchange unit 2530, 2630 intothe ablation catheter (not shown) for use in the ablation procedure.

FIG. 27 illustrates the unassembled first filter member 2720 of thevapor ablation system of FIG. 23, depicting the filter 2722 positionedwithin. In one embodiment, the first filter member 2720 includes aproximal portion 2721, a distal portion 2723, and a filter 2722. Theproximal portion 2721 and distal portion 2723 secure together and holdthe filter 2722 within. Also depicted in FIG. 27 are the disposable,single use sterile fluid container 2705 and the first length of steriletubing 2707 connecting the container 2705 to the proximal portion 2721of the first filter member 2720.

FIG. 28 illustrates one embodiment of the microcontroller 2800 of thevapor ablation system of FIG. 23. In various embodiments, themicrocontroller 2800 includes a plurality of control wires 2828connected to the pump and heater or heat exchange unit for controllingsaid components and a plurality of transmission wires 2847 for receivingflow, pressure, and temperature information from optional sensorspositioned proximate the distal end of the ablation catheter.

FIG. 29 illustrates one embodiment of a catheter assembly 2950 for usewith the vapor ablation system of FIG. 23. Vapor is delivered from theheater or heat exchange unit to the catheter assembly 2950 via a tube2948 attached to the proximal end of a connector component 2952 of theassembly 2950. A disposable catheter 2956 with a fixedly attacheddisposable length of flexible tubing 2958 at its distal end is fittedover the connector component 2952. A second filter member 2954 ispositioned between the connector component 2952 and the disposablecatheter 2956 for purifying the vapor supplied by the heater or heatexchange unit. The connector component 2952 includes two washers 2953positioned apart a short distance at its distal end to engage theoverlaying disposable catheter 2956 and form a double-stage seal,thereby preventing vapor leakage between the components. Once thedisposable catheter 2956 has been fitted to the distal end of theconnector component 2952, a catheter connector 2957 is slid over thedisposable flexible tubing 2958 and disposable catheter 2956 and is thensnapped into place onto the connector component 2952. The catheterconnector 2957 acts to keep the disposable catheter 2956 in place andalso assists in preventing vapor leakage. In various embodiments, thedisposable flexible tubing 2958 includes one or more holes or ports 2959at or proximate its distal end for the delivery of ablative vapor totarget tissues. Optionally, in one embodiment, the disposable catheter2957 includes at least one inflatable positioning member 2960 proximateits distal end.

FIG. 30 illustrates one embodiment of a heat exchange unit 3030 for usewith the vapor ablation system of FIG. 23. The heat exchange unit 3030comprises a length of coiled tubing 3035 surrounded by a heating element3034. Water 3032 enters the coiled tubing 3035 of the heat exchange unit3030 at an entrance port 3033 proximate a first end of said heatexchange unit 3030. As the water 3032 flows within the coiled tubing3035, it is converted into vapor (steam) 3038 by the heat emanating fromsaid coiled tubing 3035 which has been heated by the heating element3034. The vapor 3038 exits the coiled tubing 3035 of the heat exchangeunit 3030 at an exit port 3037 proximate a second end of said heatexchange unit 3030 and is then delivered to the ablation catheter (notshown) for use in the ablation procedure.

FIG. 31A illustrates another embodiment of a heat exchange unit 3160 foruse with the vapor ablation system of the present specification. In thepictured embodiment, the heat exchange unit 3160 comprises acylindrically shaped, pen sized ‘clamshell’ style heating block. Theheating block of the heat exchange unit 3160 includes a first half 3161and a second half 3162 fixedly attached by a hinge 3163 along one side,wherein the halves 3161, 3162 fold together and connect on the oppositeside. In one embodiment, the sides of the halves opposite the sides withthe hinge include a clasp for holding the two halves together. In oneembodiment, one of the halves includes a handle 3164 for manipulatingthe heat exchange unit 3160. When the halves are folded together, theheat exchange unit 3160 snugly envelopes a cylindrically shaped catheterfluid heating chamber 3151 attached to, in-line and in fluidcommunication with, the proximal end of the ablation catheter 3150. Eachhalf 3161, 3162 of the heat exchange unit 3160 includes a plurality ofheating elements 3165 for heating the block. In various embodiments,heat is transferred from the heating elements 3165 to the catheter fluidheating chamber 3151 using resistive or RF heating. The positioning andfit of the heating block place it in close thermal contact with thecatheter fluid heating chamber 3151. When in operation, the heatingelements 3165 heat the heating block which transfers heat to thecatheter fluid heating chamber 3151, which in turn heats the waterinside the chamber 3151, converting said water to vapor. The heatingblock does not directly contact the water. In one embodiment, thecatheter fluid heating chamber 3151 comprises a plurality of linearindentations 3191 stretching along the length of the component and inparallel with the heating elements 3165. Upon closing the halves 3161,3162, the heating elements 3165, which optionally protrude from theinternal surfaces of the halves 3161, 3162 contact, and fit within, thelinear indentations 3191. This also increases the surface area ofcontact between the heating block and the heating chamber, improving theefficiency of heat exchange. In another embodiment, the heat exchangeunit 3160 uses induction heating to convert water in the heating chamber3151 into vapor. The heating block includes an induction coil, which,when energized with electrical energy, causes heat to be generated in ametal core contained in the heating chamber 3151, as described in detailbelow. The catheter 3150 and heating chamber 3150 are single use anddisposable, allowing for ease and lowered cost of manufacture. The outersurface of the heating block itself, comprising the two halves 3161,3162, does not become heated and its temperature remains below 100° C.so it does not injure the operator.

A luer fitting coupler 3149 is provided at the proximal end of thecatheter fluid heating chamber 3151 for connecting a tube supplyingsterile water. In one embodiment, a one-way valve is included at theproximal end of the catheter fluid heating chamber 3151, distal to theluer fitting 3149, to prevent the passage of vapor under pressure towardthe water supply.

FIG. 31B illustrates another embodiment of a heat exchange unit 3170 foruse with the vapor ablation system of the present specification. Theheat exchange unit 3170 of FIG. 31B functions similarly to the heatexchange unit 3160 pictured in FIG. 31A. However, rather than having anopen design capable of opening and closing, heat exchange unit 3170 hasa closed design and is configured to slide over the catheter fluidheating chamber 3151. In one embodiment, the heat exchange unit 3170includes a handle 3174 for manipulation of said unit about the catheter3150.

As described above, the catheter fluid heating chamber is designed aspart of the ablation catheter and, along with the remainder of thecatheter, is single use and disposable. In another embodiment, thechamber is reusable, in which case the luer fitting is positioned inbetween the catheter shaft and the chamber. The heating block isdesigned to be axially aligned with the heating chamber when in use, isreusable, and will not be damaged in the event that it falls to thefloor. In one embodiment, the weight and dimensions of the heating blockare designed such that it can be integrated into a pen-sized and shapedhandle of the ablation catheter. The handle is thermally insulated toprevent injury to the operator.

In one embodiment, the heating block receives its power from a consolewhich is itself line powered and designed to provide 700-1000 W ofpower, as determined by the fluid vaporization rate. The heating blockand all output connections are electrically isolated from line voltage.In one embodiment, the console includes a user interface allowingadjustment of power with a commensurate fluid flow rate. In addition, inone embodiment, a pump, such as a syringe pump, is used to control theflow of fluid to the heating chamber and heating element. In oneembodiment, the volume of the syringe is at least 10 ml and is ideally60 ml.

FIG. 31C illustrates a heat exchange unit 3180 and catheter 3150 with asyringe pump operationally coupled to a fluid filled syringe 3155, inaccordance with one embodiment of the present specification. A fluidheating chamber 3151 is depicted within the heat exchange unit 3180 atthe proximal end of the catheter 3150. In various embodiments, the heatexchange unit 3180 is similar to the heat exchange units depicted inFIGS. 31A and 31B. Referring to FIG. 31C, the catheter 3150 alsoincludes a positioning balloon 3152 at its distal end and aninsufflation port 3153 at its proximal end for inflating the balloon3152. An insulating handle 3154 covers a proximal portion of thecatheter 3150 where the insufflation port 3153 joins with the catheter3150 allowing for the operator to manipulate the catheter withoutgetting injured by the thermal energy. A syringe 3155 attaches to theproximal end of the heating chamber 3151 to provide fluid, such aswater, to the heating chamber 3151. In another embodiment, the syringe3155 is pre-attached to the proximal end of the heating chamber 3151 toprovide fluid, such as water, to the heating chamber 3151 in order toprevent leakage of the fluid. The syringe 3155 includes a plunger 3156at its distal end. In various embodiments, the plunger 3156 is ahandle-less disc-shaped plunger and has a diameter matching a diameterof the syringe 3155. The fluid is converted into vapor in the heatingchamber 3151 as a result of the transfer of thermal energy into theheating chamber 3151 from the surrounding heat exchange unit 3180. Thevapor is delivered from the distal end of the catheter 3150 to ablate atarget tissue.

In the above embodiment, the catheter to be used with the vapor ablationsystem is designed using materials intended to minimize cost. In oneembodiment, the tubing used with the catheter is able to withstand atemperature of at least 125° C. and can flex through an endoscope's bendradius (approximately 1 inch) without collapse. In one embodiment, thesection of the catheter that passes through an endoscope is 7 French(2.3 mm) diameter and has a minimum length of 215 cm. In one embodiment,thermal resistance is provided by the catheter shaft material whichshields the endoscope from the super-heated vapor temperature. In oneembodiment, the heat exchange unit is designed to interface directlywith, or in very close proximity to, an endoscope's biopsy channel tominimize the likelihood of a physician handling heated components.Having the heat exchange unit in close proximity to the endoscope handlealso minimizes the length of the catheter through which the vapor needsto travel, thus minimizing heat loss and premature condensation.

In various embodiments, other means are used to heat the fluid withinthe catheter fluid heating chamber. FIG. 32A illustrates the use ofinduction heating to heat a chamber 3205. When an alternating electriccurrent 3202 is passed through a coil 3207 of wire within the chamber3205, the coil 3207 creates a magnetic field 3209. Magnetic lines offlux 3210 of the magnetic field 3209 cut through the air around the coil3207. When the chamber 3205 is composed of a ferrous material, such as,iron, stainless steel, or copper, electrical currents known as eddycurrents 3215 are induced to flow in the chamber 3205 as a result of thepresence of the alternating current 3202 and magnetic field 3209 withlines of flux 3210. The eddy currents 3215 cause localized heating ofthe chamber 3205. When the chamber 3205 is filled with a fluid, such aswater, the heat is transferred from the chamber to the fluid inside,resulting in vaporization of said fluid. In the embodiment depicted inFIG. 32A, the coil 3207 is looped about the chamber 3205 with four loopsand spaced a distance away from said chamber 3205 to assist withvisualization. The design of the chamber and coil in FIG. 32A depictsonly one possible embodiment and is not intended to be limiting. Thoseskilled in the art will understand many different design configurationsare possible with respect to the chamber and coil. In variousembodiments, the coil includes at least one loop about the chamber andis looped about said chamber such that the coil is in physical contactwith said chamber. In other embodiments, the coil includes at least oneloop about the chamber and is looped about said chamber such that thecoil is spaced away a specific distance from said chamber with a layerof air or other insulating material between said coil and said chamber.In various embodiments, the loops of the coil are arranged closelytogether such that they are in contact with one another. In otherembodiments, the loops of the coil are arranged with a specific distancebetween one another. In one embodiment, the loops of the coil extendalong the entire length of the chamber. In various embodiments, theloops of the coil extend beyond the length of the chamber. In otherembodiments, the loops of the coil extend along a portion of the lengthof the chamber that is less than the chamber's total length.

FIG. 32B is a flow chart listing the steps involved in using inductionheating to heat a chamber. At step 3252, a metal coil is placed about achamber composed of a ferromagnetic material such that the coilsurrounds the chamber. Then, at step 3254, the chamber is filled with afluid via a proximal inlet port on said chamber. At step 3256, analternating current is provided to the coil, creating a magnetic fieldin the area surrounding the chamber. The magnetic field induces electric(eddy) current flow in the ferromagnetic material which heats thechamber. The heat is transferred to the fluid inside the chamber andvaporizes the fluid. The vaporized fluid exits the chamber via thedistal outlet port.

FIG. 33A illustrates one embodiment of a coil 3370 used with inductionheating in the vapor ablation system of the present specification. Asection of the coil 3370 has been cut away to assist with visualization.The coil 3370 is positioned surrounding the catheter fluid heatingchamber 3351. An alternating current 3302 passing through the coil 3370creates a magnetic field which induces eddy currents 3315 to flow in thechamber 3370 as described above. The flow of eddy currents 3315 resultsin heating of the catheter fluid heating chamber 3351. The heatedchamber heats the fluid within, converting it into a vapor, which passesinto the catheter 3350 for use in the ablation procedure. The catheter3350 includes at least one delivery port 3352 at its distal end for thedelivery of vapor. Optionally, the catheter 3350 includes at least onepositioning element 3353 proximate its distal end. In one embodiment,the at least one positioning element 3353 is an inflatable balloon. Thecoil 3370 itself does not heat, making it safe to touch. A luer fittingcoupler 3349 is provided at the proximal end of the catheter fluidheating chamber 3351 for connecting a tube supplying sterile water. Inone embodiment, a one-way valve (not shown) is included at the proximalend of the catheter fluid heating chamber 3351, distal to the luerfitting 3349, to prevent the passage of vapor toward the water supply.In one embodiment, thermal insulating material (not shown) is positionedbetween the coil 3370 and the heating chamber 3351. In anotherembodiment, the chamber 3351 is suspended in the center of the coil 3370with no physical contact between the two. In this embodiment, theintervening air acts as a thermally insulating material. The design ofthe chamber is optimized to increase its surface area to maximizecontact and heat transfer, in turn resulting in more efficient vaporgeneration. In one embodiment, the coil 3370 is constructed in a‘clamshell’ style design, similar to the heat exchange unit 3160depicted in FIG. 31A, and opens and closes about the heating chamber3351. In another embodiment, the coil 3370 is constructed in a closedstyle design, similar to the heat exchange unit 3170 depicted in FIG.31B, and slides over the heating chamber 3351.

In various embodiments, the induction heating systems and structuresdescribed in FIGS. 32A and 33A can be applied to any of the fluidchambers shown in any of the disclosed embodiments of the presentspecification.

FIG. 33B illustrates one embodiment of a catheter handle 3372 used withinduction heating in the vapor ablation system of the presentspecification. The handle 3372 is thermally insulated and incorporatesan induction coil. In one embodiment, the handle 3372 includes aninsulated tip 3373 at its distal end that engages with an endoscopechannel after the catheter is inserted into the endoscope. The catheter3350 is connected to the heating chamber 3351 which in turn is connectedwith the pump via an insulated connector 3374. In one embodiment, theheating chamber 3351 length and diameter are less than those of thehandle 3372 and the induction coil, thus the heating chamber 3351 canslide inside the handle 3372 in a coaxial fashion while maintaining aconstant position within the magnetic field generated by the inductioncoil. The operator can manipulate the catheter 3350 by grasping on theinsulated connector 3374 and moving it in and out of the handle 3372which in turn moves the catheter tip in and out of the distal end of theendoscope. In this design, the heated portions of the catheter 3350 arewithin the channel of the endoscope and in the insulated handle 3372,thus not coming into contact with the operator at anytime during theoperation. An optional sensor 3375 on the insulated tip 3373 can sensewhen the catheter is not engaged with the endoscope and temporarilydisable the heating function of the catheter to prevent accidentalactivation and thermal injury to the operator. With respect to FIG. 33B,the catheter 3350 and heating chamber 3351 are the heated components ofthe system while the handle 3372, insulated tip 3373, and insulatedconnector 3374 are the cool components and therefore safe to touch bythe user. The catheter 3350 includes at least one delivery port 3352 atits distal end for the delivery of vapor. Optionally, the catheter 3350includes at least one positioning element 3353 proximate its distal end.In one embodiment, the at least one positioning element 3353 is aninflatable balloon.

FIG. 33C illustrates a disassembled coil component 3311 and heatingchamber 3312 of an induction heating system 3310 in accordance with oneembodiment of the present specification. In some embodiments, the coilcomponent 3311 comprises an induction coil support structure in the formof an outer shell or bobbin 3309 with an electromagnetic coil 3317wrapped thereabout. The induction coil support structure/bobbin 3309supports the induction coil 3317 and slidably receives the heatingchamber 3312. In other embodiments, the coil component 3311 comprisesonly a coil 3317. In some embodiments, the coil 3317 comprises solidcopper wire. In other embodiments, the coil 3317 comprises copper tubingto allow for water cooling through the tubing. In various embodiments,the copper wire or copper tubing is mechanically self-supporting (nobobbin required) due to the stiffness of the wire or tubing and has fewwindings. In some embodiments, the copper wire or copper tubing has 10winding with space between each winding so that insulation may beomitted. In still other embodiments, the coil 3317 comprisesmulti-strand litz wire having hundreds of individual strands insulatedfrom one another to counter the skin effect and allow for low-losshigh-frequency operation. In some embodiments, the individual wires areAWG46 strands. In embodiments where the coil 3317 comprises multi-strandlitz wire, a bobbin 3309 is required for supporting and winding the coil3317 thereabout. A wire 3319 is attached to the coil 3317 for providingthe coil 3317 with radiofrequency (RF) energy. In some embodiments, thewire 3319, providing an electrical connection to the induction heatingsystem 3310, is coupled with a fluid connector supplying fluid to thevapor delivery system. Coupling the electrical connection with the fluidconnection simultaneously provides a mechanically stable fluidconnection and connection of the RF coil with wires from a generator tocomplete an electrical circuit. This coupling functions as a failsafe asincomplete fluid connection would result in no electrical connection andthe induction heating would not be switched on. The coil component 3311has an elongate shape with a proximal end and a distal end and furtherincludes an opening 3313 at its proximal end configured to receive theheating chamber 3312. The heating chamber 3312 comprises an innerelectrically conducting or ferromagnetic core 3314 and includes an inletport 3318 at its proximal end for connecting to a fluid source and anoutlet port 3316 at its distal end for the delivery of generated steam.A space 3355 is present between the core 3314 and the walls of theheating chamber 3312 where heat energy from the core 3314 is transferredto fluid within the chamber 3312 to convert the fluid to steam.

FIG. 33D illustrates an assembled induction heating system 3310comprising the coil component 3311 and heating chamber 3312 of FIG. 33C.The heating chamber 3312 has been inserted through opening 3313 and ismovable longitudinally within the coil component 3311. RF energysupplied by the wire 3319 to the coil 3317 is converted to a magneticfield about the coil 3317 which, through eddy current losses andmagnetic hysteresis losses, induces the creation of heat energy withinthe core 3314. Fluid supplied at input port 3318 is converted to steamby the heat energy in space 3355 within the heating chamber 3312 andexits via outlet port 3316.

In some embodiments, referring to FIGS. 33C and 33D simultaneously, theinduction heating system 3310 further includes a mechanism formaintaining the heating chamber 3312 within the coil component 3311 onceassembled, while still allowing for some coaxial movement of the heatingchamber 3312 within the coil component. In some embodiments, referringto FIG. 33C, a first stopping mechanism 3358 comprises a portion of thecoil 3317 which has been positioned in a plane defined by opening 3313.The first stopping mechanism 3358 functions as a mechanical limiter sothat the heating chamber 3312 may be slid into the coil component 3311from a proximal end and then comes against the stopping mechanism 3358at the distal end, preventing further movement in a distal direction. Inother embodiments, a second stopping mechanism 3359 is provided on theproximal end of the bobbin 3309. In various embodiments, the secondstopping mechanism comprises a luer lock or other connector. In someembodiments, the second stopping mechanism 3359 is similar to the springloaded connector depicted in FIGS. 33R and 33S. A portion of the secondstopping mechanism 3359 extends into opening 3313. To insert the heatingchamber 3312 into the coil component 3311, the second stopping mechanism3359 is depressed, causing said extending portion to retract andproviding a complete opening 3313. The heating chamber 3312 is slid intothe coil component 3311 through the opening 3313 at the proximal end ofthe coil component 3311 while the second stopping mechanism 3359 isdepressed. Once the heating chamber 3312 has been fully inserted, thesecond stopping mechanism 3359 is released and the extending portionextends again into opening 3313, acting as a stopper for the heatingchamber 3312 in the proximal direction. In some embodiments, theinduction heating system 3310 includes both a first stopping mechanism3358 and a second stopping mechanism 3359 wherein a distance betweensaid first stopping mechanism 3358 and said second stopping mechanism3359 is greater than a length of the heating chamber 3312 to allow forsome coaxial movement of the heating chamber 3312 within the coilcomponent 3311. In other embodiments, the induction heating system 3310includes only a first stopping mechanism 3358. In still otherembodiments, the induction heating system 3310 includes only a secondstopping mechanism 3359. In various embodiments, the heating chamber3312 can move coaxially within the coil component 3311 a distance equalto at least 5% of a length of the coil 3317. In various embodiments, thecoil component 3311 and heating chamber 3312 can move coaxially within ahandle, such as handle 3372 of FIG. 33B, a distance equal to at least 5%of a length of the handle. In some embodiments, one or both of theheating chamber 3312 and coil component 3311 are disposable. In someembodiments, the heating induction system 3310 further includes a sensor3371 configured to sense a parameter of the system 3310 and inform auser that it is safe to disconnect the heating chamber 3312 from thecoil component 3311. For example, in an embodiment, the sensor 3371 is atemperature sensor which senses a temperature of the heating inductionsystem 3310 and signals the user when the system temperature hasdecreased sufficiently that the heating chamber 3312 is safe to touchwithout burn risk and can be removed from the coil component 3311. Invarious embodiments, other heating chamber and coil componentembodiments discussed below also include first stopping mechanisms,second stopping mechanisms, and sensors as described with reference toFIGS. 33C and 33D. In some embodiments, the heating chamber and coil ofFIGS. 33C and 33D are similar to those described with reference to FIGS.49K through 49M.

FIGS. 33E and 33F illustrate a first conventional endoscope handle 3340and a second conventional endoscope handle 3344 respectively, for usewith an induction heating system of the present specification. Theendoscope handles 3340, 3344 include, among other controls, an air/waterbutton 3341, 3346 to provide air or fluid to a body lumen, a suctionbutton 3342, 3347 to provide suction to a body lumen, and a biopsy orworking channel 3343, 3348 for the insertion of working tools andremoval or body tissues. In various embodiments of the presentspecification, an induction heating system, such as those discussedbelow with reference to FIGS. 33G through 33S, is connected to thebiopsy or working channel 3343, 3348 to provide steam to a body lumen.

FIG. 33G illustrates a dissembled coil component 3321 and heatingchamber 3322 of an induction heating system 3320 for use with anendoscope, in accordance with one embodiment of the presentspecification. In some embodiments, the coil component 3321 comprises anouter shell with an electromagnetic coil 3327. In other embodiments, thecoil component 3321 comprises only a coil 3327. A wire 3329 is attachedto the coil 3327 for providing the coil 3327 with radiofrequency (RF)energy. The coil component 3321 has an elongate shape with a proximalend and a distal end and further includes an opening 3323 at itsproximal end configured to receive the heating chamber 3322 and aconnector 3325 at its distal end configured to attach to a workingchannel port of an endoscope. The heating chamber 3322 comprises aninner electrically conducting or ferromagnetic core 3324 and includes aninlet port 3328 at its proximal end for connecting to a fluid source anda catheter 3326 at its distal end for the delivery of generated steam. Aspace 3345 is present between the core 3324 and the walls of the heatingchamber 3322 where heat energy from the core 3324 is transferred tofluid within the chamber 3322 to convert the fluid to steam.

FIG. 33H illustrates an assembled induction heating system 3320 for usewith an endoscope comprising the coil component 3321 and heating chamber3322 of FIG. 33G. The heating chamber 3322 has been inserted throughopening 3323 and is movable longitudinally within the coil component3321. The catheter 3326 has been passed through connector 3325 and isconfigured to extend along the length of the working channel of anendoscope. Movement of the heating chamber 3322 relative to the coilcomponent 3321 allows for positioning of the catheter 3326 within a bodylumen. RF energy supplied by the wire 3329 to the coil 3327 is convertedto a magnetic field about the coil 3327 which, through eddy currentlosses and magnetic hysteresis losses, induces the creation of heatenergy within the core 3324. Fluid supplied at input port 3328 isconverted to steam by the heat energy in space 3345 within the heatingchamber 3322 and exits via catheter 3326.

FIG. 33I illustrates a dissembled coil component 3331 and heatingchamber 3332 of an induction heating system 3330 for use with anendoscope, in accordance with another embodiment of the presentspecification. In some embodiments, the coil component 3331 comprises anouter shell with an electromagnetic coil 3337. In other embodiments, thecoil component 3331 comprises only a coil 3337. A wire 3339 is attachedto the coil 3337 for providing the coil 3337 with radiofrequency (RF)energy. The coil component 3321 has an elongate shape with a proximalend and a rounded distal end and further includes an opening 3333 at itsproximal end configured to receive the heating chamber 3332 and aconnector 3335 at its distal end configured to attach to a workingchannel port of an endoscope. The heating chamber 3332 comprises aninner electrically conducting or ferromagnetic core 3334 and includes aninlet port 3338 at its proximal end for connecting to a fluid source anda catheter 3336 at its distal end for the delivery of generated steam.The distal end of the heating chamber 3332 is rounded to fit within therounded distal end of the coil component 3331. A space 3377 is presentbetween the core 3334 and the walls of the heating chamber 3332 whereheat energy from the core 3334 is transferred to fluid within thechamber 3332 to convert the fluid to steam. The heating chamber 3332further includes a grasper 3376 for manipulating the chamber 3332 andmoving the chamber 3332 and core 3334 relative to the coil component3331.

FIG. 33J illustrates an assembled induction heating system 3330 for usewith an endoscope comprising the coil component 3331 and heating chamber3332 of FIG. 33I. The heating chamber 3332 has been inserted throughopening 3333 and is movable longitudinally within the coil component3331. The catheter 3336 has been passed through connector 3335 and isconfigured to extend along the length of the working channel of anendoscope. Movement of the heating chamber 3332 relative to the coilcomponent 3331 via manipulation of the grasper 3376 allows forpositioning of the catheter 3336 within a body lumen. RF energy suppliedby the wire 3339 to the coil 3337 is converted to a magnetic field aboutthe coil 3337 which, through eddy current losses and magnetic hysteresislosses, induces the creation of heat energy within the core 3334. Fluidsupplied at input port 3338 is converted to steam by the heat energy inspace 3377 within the heating chamber 3332 and exits via catheter 3336.

FIG. 33K illustrates an induction heating system 3380 comprising ahandle 3386 configured to be attached to a conventional endoscopehandle, in accordance with one embodiment of the present specification.The induction heating system handle 3386 includes at least one clamp3381 for securing the induction heating system 3380 to an endoscopehandle. In one embodiment, the inductions heating system includes twoclamps 3381, one each at a proximal and distal end of the handle 3386.The coil component 3384 is embedded within the handle 3386 and movablelongitudinally about a heating chamber (not shown) by manipulation of awheel mechanism 3383 on the handle 3386. In one embodiment, a springloaded connector 3382 at the distal end of the handle 3386 attaches theinduction heating system 3380 to a working channel port of the endoscopehandle. A catheter 3385 extends from a distal end of the heating chamberand is configured to pass through the working channel of the endoscope.An inlet port 3387 extends from a proximal end of the heating chamberfor connection to a fluid source.

FIG. 33L is a cross-sectional illustration of an induction heatingsystem 3390 comprising a handle 3396 and having a wheel mechanism 3393for moving a coil component 3394 relative to a heating chamber 3398, inaccordance with one embodiment of the present specification. The coilcomponent 3394 is embedded within the handle 3396 and movablelongitudinally about the heating chamber 3398 and core 3399 bymanipulation of a wheel mechanism 3393 on the handle 3396. A connector3392 at the distal end of the coil component 3394 attaches the inductionheating system 3390 to a working channel port of an endoscope handle. Invarious embodiments, the connector 3392 is a luer lock connector orspring loaded connector. A catheter 3395 extends from a distal end ofthe heating chamber 3398, passes through connector 3392, and isconfigured to extend through the working channel of the endoscope. Aninlet port 3397 extends from a proximal end of the heating chamber 3398for connection to a fluid source. In some embodiments, handle 3396includes at least one mechanism, similar to clamps 3381 of FIG. 33K, forattaching the induction heating system 3390 to an endoscope handle.

FIG. 33M illustrates an induction heating system 3300 comprising aheating chamber 3304 in a first position relative to a coil component3303, in accordance with one embodiment of the present specification. Inthe first position, the heating chamber 3304 is located in a most distalposition relative to the coil component 3303. The induction heatingsystem 3300 includes a handle 3306 for manipulation of the heatingchamber 3304 relative to the coil component 3303. A connector 3308 ispositioned at the distal end of the coil component 3303 for attachingthe induction heating system 3300 to a working channel port of anendoscope. The heating chamber 3304 includes an inlet port 3307 at itsproximal end for providing a fluid to the heating chamber 3304 and acatheter 3305 at its distal end configured to extend through the workingchannel of the endoscope. FIG. 33N illustrates the induction heatingsystem 3300 of FIG. 33M with the heating chamber 3304 in a secondposition relative to the coil component 3303. In the second position,the heating chamber 3304 has been moved proximally relative to the coilcomponent 3303 via manipulation of the handle 3306. The coil component3303 position remains fixed as the coil component 3303 is attached to anendoscope handle via connector 3308. Movement of the heating chamber3304 results in similar movement of the attached catheter 3305 andfine-tune positioning of the distal end of the catheter 3305 within abody lumen.

FIG. 33O illustrates an induction heating system 3360 comprising a firsthandle component 3365 in a first position relative to a second handlecomponent 3366, in accordance with one embodiment of the presentspecification. In one embodiment, the first handle component 3365 has anelongate body with a proximal end and distal end and comprises a heatingchamber within. In one embodiment, the second handle component 3366 hasan elongate body with a proximal end and a distal end and comprises acoil within. The second handle component 3366 telescopes in and out ofthe distal end of the first handle component 3365. An inlet port 3361 isincluded at the proximal end of the first handle component 3365 forproviding the heating chamber with fluid. A connector 3368 is includedat the distal end of the second handle component 3366 for attaching theinduction heating system 3360 to a working channel port of an endoscopehandle. A catheter 3362 extends through the second handle component 3366and is in fluid communication with the heating chamber within the firsthandle component 3365. In the first position depicted in FIG. 33O, thefirst handle component 3365 is positioned most proximally relative tothe second handle component 3366. The second handle component 3366includes a plurality of markings 3363 along its body. In oneembodiments, the markings 3363 are numbers. The first handle component3365 includes a window 3364 proximal its distal end which aligns withone of said markings as the first handle component 3365 is movedlongitudinally relative to the second handle component 3366. The marking3363 in the window 3364 indicates the length of the catheter 3362extended beyond the distal end of the working channel of the endoscopeand into a body lumen of a patient. FIG. 33P illustrates the inductionheating system 3360 of FIG. 33O with the first handle component 3365 ina second position relative to the second handle component 3366. Themarking 3367 in window 3364 indicates to an operator that the firsthandle component 3365 is in its most distal position relative to thesecond handle component 3366 and that the catheter 3362 is fullyextended within the body lumen of the patient.

FIG. 33Q illustrates a luer lock mechanism 3369 at a distal end of ahandle of an induction heating system 3360, in accordance with oneembodiment of the present specification. A catheter 3362 exists throughthe luer lock mechanism 3369 and is configured to extend through aworking channel of an endoscope. The luer lock mechanism 3369 isconfigured to attach to a corresponding connector at a working channelport of an endoscope handle.

FIG. 33R illustrates a spring loaded connector 3356 in a first positionat a distal end of a handle of an induction heating system 3354, inaccordance with one embodiment of the present specification. In thefirst position, the spring loaded connector 3356 is locked and securedto a working channel port of an endoscope handle. A catheter 3357extends through the distal end of the induction heating system handle.FIG. 33S illustrates the spring loaded connector 3356 of FIG. 33R in asecond position, wherein the connector 3356 is depressed and open forconnecting to a working channel port of an endoscope handle.

FIG. 33T illustrates a closed loop vapor delivery system 3300 t for usewith an endoscope, in accordance with one embodiment of the presentspecification. A closed loop catheter 3301 t, heating chamber 3302 t,and fluid channel 3303 t (from a fluid source 3306 t) is provided. Invarious embodiments, the fluid channel 3303 t comprises a solid tube orhousing and acts as a handle to be held and manipulated by a physician.The catheter 3301 t is configured to be inserted in the working channelof an endoscope, such as working channel 3343 of FIG. 33E. The heatingchamber 3302 t is positioned within an induction coil support structure3304 t which in turn, is attached via wire 3305 t, to driving circuitryto power the coil and generate induction heating. The induction coilsupport structure 3304 t supports the induction coil and slidablyreceives the heating chamber. Fluid is provided from fluid source 3306 tthrough fluid channel 3303 t and into heating chamber 3302 t where it isconverted into steam through induction heating provided by inductioncoil support structure 3304 t. The steam travels through catheter 3301 tand is delivered to a target tissue via one or more openings 3307 t atthe distal end of the catheter 3301 t. In some embodiments, the catheter3301 t further includes one or more positioning elements, for exampleinflatable balloons, for positioning the catheter 3301 t within a bodycavity. The induction coil support structure 3304 t moves with theheating chamber 3302 t. A physician holds the fluid channel 3303 t,which doubles as a handle, and moves the catheter 3301 t as needed viathe endoscope. Using this closed loop system 3300 t to deliver vapor forablation therapy comprises simply inserting the catheter 3301 t into theendoscope and moving back and forth.

FIG. 33U is a flowchart illustrating the steps involved in oneembodiment of a method of providing vapor ablation therapy using thevapor delivery system of FIG. 33T. At step 3302 u, the catheter of theclosed loop vapor delivery system in inserted into a working channel ofan endoscope. The induction coil support structure is then connected todriving circuitry via a wire at step 3304 u. The driving circuitryprovides electrical current to the coil at step 3306 u resulting ininduction heating of the heating chamber. At step 3308 u, fluid issupplied from the fluid source and through the fluid channel to theheating chamber where it is converted to steam. The physician holds thefluid channel at step 3310 u and moves the closed loop system within theendoscope channel or moves the entire endoscope to position the distalend of the catheter proximate a target tissue for vapor ablation.

FIG. 33V illustrates a closed loop vapor delivery system 3300 v for usewith an endoscope, in accordance with another embodiment of the presentspecification. A closed loop catheter 3301 v, heating chamber 3302 v,and fluid channel 3303 v (from a fluid source 3306 v) is provided. Invarious embodiments, the fluid channel 3303 v comprises a solid tube orhousing and acts as a handle to be held and manipulated by a physician.In this embodiment, the heating chamber 3302 v is too big to be movedback and forth without support. Therefore, the system 3300 v includes anendoscope handle attachment 3308 v, similar to the handle 3386 shown inFIG. 33K. The catheter 3301 v is configured to be inserted into theworking channel of an endoscope, such as working channel 3343 of FIG.33E, with the heating chamber 3302 v and handle portion of the fluidchannel 3303 v being positioned within the endoscope handle attachment3308 v. In the embodiment depicted in FIG. 33V, the endoscope handleattachment 3308 v has the induction coil built-in. The built-in coil isin turn attached to driving circuitry via wire 3305 v to power the coiland generate induction heating. Fluid is provided from fluid source 3306v through fluid channel 3303 v and into heating chamber 3302 v where itis converted into steam through induction heating provided by thebuilt-in coil of the endoscope handle attachment 3308 v. The steamtravels through catheter 3301 v and is delivered to a target tissue viaone or more openings 3307 v at the distal end of the catheter 3301 v. Insome embodiments, the catheter 3301 v further includes one or morepositioning elements, for example inflatable balloons, for positioningthe catheter 3301 v within a body cavity. The endoscope handleattachment 3308 v does not move with the heating chamber 3302 v. Aphysician toggles a switch on the endoscope handle attachment 3308 vwhich manipulates the fluid channel 3302 v, which doubles as a handle,and moves the catheter 3301 v as needed via the endoscope. In thisembodiment, the closed loop system 3300 v inserted into the endoscope ismoved back and forth and the heating chamber 3302 v remains in the fieldgenerated by the stationary induction coil in the endoscope handleattachment 3308 v.

FIG. 33W is a flowchart illustrating the steps involved in oneembodiment of a method of providing vapor ablation therapy using thevapor delivery system of FIG. 33V. At step 3302 w, the catheter of theclosed loop vapor delivery system in inserted into a working channel ofan endoscope. The endoscope handle attachment, containing the built-incoil, is then connected to driving circuitry via a wire at step 3304 w.The driving circuitry provides electrical current to the coil at step3306 w resulting in induction heating of the heating chamber. At step3308 w, fluid is supplied from the fluid source and through the fluidchannel to the heating chamber where it is converted to steam. Thephysician toggles a switch on the endoscope handle attachment at step3310 w which moves the catheter within the endoscope channel or movesthe entire endoscope to position the distal end of the catheterproximate a target tissue for vapor ablation.

FIG. 33X illustrates a closed loop vapor delivery system 3300 x for usewith an endoscope, in accordance with yet another embodiment of thepresent specification. A closed loop catheter 3301 x, heating chamber3302 x, and fluid channel 3303 x (from a fluid source 3306 x) isprovided. In various embodiments, the fluid channel 3303 x comprises asolid tube or housing and acts as a handle to be held and manipulated bya physician. In this embodiment, the heating chamber 3302 x is too bigto be moved back and forth without support. Therefore, the system 3300 xincludes an endoscope handle attachment 3308 x, similar to the handle3386 shown in FIG. 33K. The catheter 3301 x is configured to be insertedinto the working channel of an endoscope, such as working channel 3343of FIG. 33E, with the heating chamber 3302 x and handle portion of thefluid channel 3303 x being positioned within the endoscope handleattachment 3308 x. In the embodiment depicted in FIG. 33X, the inductioncoil 3309 x is attached to and wound about the heating chamber 3302 xand is not included as a part of the endoscope handle attachment 3308 x.The induction coil 3309 x is in turn attached to driving circuitry viawire 3305 x to power the coil 3309 x and generate induction heating.Fluid is provided from fluid source 3306 x through fluid channel 3303 xand into heating chamber 3302 x where it is converted into steam throughinduction heating provided by the induction coil 3309 x. The steamtravels through catheter 3301 x and is delivered to a target tissue viaone or more openings 3307 x at the distal end of the catheter 3301 x. Insome embodiments, the catheter 3301 x further includes one or morepositioning elements, for example inflatable balloons, for positioningthe catheter 3301 x within a body cavity. The endoscope handleattachment 3308 x does not move with the heating chamber 3302 x,however, the heating chamber 3302 x and induction coil 3309 x do movetogether as they are physically attached to one another. A physiciantoggles a switch on the endoscope handle attachment 3308 x whichmanipulates the fluid channel 3302 x, which doubles as a handle, andmoves the catheter 3301 x as needed via the endoscope. In thisembodiment, the closed loop system 3300 x inserted into the endoscope ismoved back and forth and the heating chamber 3302 x and attachedinduction coil 3309 x move together relative to the endoscope handleattachment 3308 x.

FIG. 33Y is a flowchart illustrating the steps involved in oneembodiment of a method of providing vapor ablation therapy using thevapor delivery system of FIG. 33X. At step 3302 y, the catheter of theclosed loop vapor delivery system in inserted into a working channel ofan endoscope. The induction coil, attached to the heating chamber, isthen connected to driving circuitry via a wire at step 3304 y. Thedriving circuitry provides electrical current to the coil at step 3306 yresulting in induction heating of the heating chamber. At step 3308 y,fluid is supplied from the fluid source and through the fluid channel tothe heating chamber where it is converted to steam. The physiciantoggles a switch on the endoscope handle attachment at step 3310 y whichmoves the catheter within the endoscope channel or moves the entireendoscope to position the distal end of the catheter proximate a targettissue for vapor ablation.

FIGS. 34A and 34B are front and longitudinal view cross sectionaldiagrams respectively, illustrating one embodiment of a catheter 3480used with induction heating in the vapor ablation system of the presentspecification. The catheter 3480 includes an insulated handle 3486 thatcontains a heating chamber 3451 and an induction coil 3484. The heatingchamber 3451 includes a luer lock 3449 at its proximal end. The luerlock 3449 has a one-way valve that prevents the backward flow of vaporfrom the chamber 3451. Vaporization of fluid in the chamber results involume expansion and an increase in pressure which pushes the vapor outof the chamber 3451 and into the catheter body. The induction coil 3484includes a wire 3485 that extends from the proximal end of the catheter3480 for the delivery of an alternating current. The handle 3486 isconnected to the catheter 3480 with an outer insulating sheath 3481 madeof a thermally insulating material.

In various embodiments, the insulating material is polyether etherketone (PEEK), polytetrafluoroethylene (PTFE), fluorinated ethylenepropylene (FEP), polyether block amide (PEBA), polyimide, ceramic, or asimilar material. In various embodiments, optional sensors 3487positioned proximate the distal end of the catheter 3480 measure one ormore of temperature, pressure, or flow of vapor and transmit theinformation to a microprocessor, which in turn controls the flow rate ofthe fluid and the level of vaporizing energy provided to the chamber3451. The microcontroller adjusts fluid flow rate and chambertemperature based on the sensed information, thereby controlling theflow of vapor and in turn, the flow of ablative energy to the targettissue.

In one embodiment, the catheter 3480 includes an inner flexible metalskeleton 3483. In various embodiments, the skeleton 3483 is composed ofcopper, stainless steel, or another ferric material. The skeleton 3483is in thermal contact with the heating chamber 3451 so that the heatfrom the chamber 3451 is passively conducted through the metal skeleton3483 to heat the inside of the catheter 3480, thus maintaining the steamin a vaporized state and at a relatively constant temperature. Invarious embodiments, the skeleton 3483 extends through a particularportion or the entire length of the catheter 3480. In one embodiment,the skeleton 3483 includes fins 3482 at regular intervals that keep theskeleton 3483 in the center of the catheter 3480 for uniform heating ofthe catheter lumen.

In another embodiment, as seen in FIG. 34C, the catheter includes aninner metal spiral 3488 in place of the skeleton. In yet anotherembodiment, as seen in FIG. 34D, the catheter includes an inner metalmesh 3489 in place of the skeleton. Referring to FIGS. 34B, 34C, and 34Dsimultaneously, water 3432 enters the luer lock 3449 at a predeterminedrate. It is converted to vapor 3438 in the heating chamber 3451. Themetal skeleton 3483, spiral 3488, and mesh 3489 all conduct heat fromthe heating chamber 3451 into the catheter lumen to prevent condensationof the vapor in the catheter and insure that ablating vapor will exitthe catheter from one or more holes or ports at its distal end.

FIG. 35 illustrates one embodiment of a heating unit 3590 usingmicrowaves 3591 to convert fluid to vapor in the vapor ablation systemof the present specification. The microwaves 3591 are directed towardthe catheter fluid heating chamber 3551, heating the chamber 3551 andconverting the fluid within into vapor. The vapor passes into thecatheter 3550 for use in the ablation procedure. The catheter 3550includes at least one delivery port 3552 at its distal end for thedelivery of vapor. A luer fitting coupler 3549 is provided at theproximal end of the catheter fluid heating chamber 3551 for connecting atube supplying sterile water. In one embodiment, a one-way valve (notshown) is included at the proximal end of the catheter fluid heatingchamber 3551, distal to the luer fitting 3549, to prevent the passage ofvapor toward the water supply.

In various embodiments, other energy sources, such as, High IntensityFocused Ultrasound (HIFU) and infrared energy, are used to heat thefluid in the catheter fluid heating chamber.

FIG. 36A illustrates a catheter assembly having an inline chamber 3610for heat transfer in accordance with one embodiment of the presentspecification and FIG. 36B illustrates the catheter assembly of FIG. 36Aincluding an optional handle 3630. Referring to FIGS. 36A and 36Bsimultaneously, the assembly includes a catheter 3605 having an elongatebody with a lumen within, a proximal end, and a distal end. The catheter3605 includes at least one delivery port 3606 at its distal end for thedelivery of vapor. A first inline chamber 3610, having an elongate bodywith a lumen within, a proximal end and a distal end, is attached at itsdistal end to the proximal end of the catheter 3605. In variousembodiments, the first inline chamber 3610 is composed of aferromagnetic substance or a thermally conducting substance. The lumenof the catheter 3605 is in fluid communication with the lumen of thefirst inline chamber 3610. A second inline chamber 3620, having anelongate body with a lumen within, a proximal end and a distal end, isattached at its distal end to the proximal end of the first inlinechamber 3610. The second inline chamber 3620 is filled with a fluid. Thelumen of the first inline chamber 3610 is in fluid communication withthe lumen of the second inline chamber 3620. In one embodiment, theconnection between the first inline chamber 3610 and the second inlinechamber 3620 includes an optional occlusion member 3615 to control theflow of fluid from said second inline chamber 3620 to said first inlinechamber 3610. In one embodiment, the occlusion member 3615 comprises amembrane positioned between the first inline chamber 3610 and the secondinline chamber 3620 which functions to prevent flow of the fluid fromthe second inline chamber 3620 into the first inline chamber 3610 untiltherapy is ready to be delivered. As pressure is applied to the fluid inthe second inline chamber 3620 by action of a piston 3625, said pressureis transmitted to the membrane, resulting in rupture of the membrane.The fluid is then allowed to flow from the second inline chamber 3620into the first inline chamber 3610.

In another embodiment, the occlusion member 3615 comprises a valve. Aspressure is applied to the fluid in the second inline chamber 3620 byaction of the piston 3625, said pressure is transmitted to the valve,resulting in opening of the valve. The fluid is then allowed to flowfrom the second inline chamber 3620 into the first inline chamber 3610.In yet another embodiment, the occlusion member 3615 comprises a heatsensitive plug. As the temperature in the first inline chamber 3610rises above a predetermined level, the plug melts and the fluid isallowed to flow from the second inline chamber 3620 into the firstinline chamber 3610. In another embodiment, the heat sensitive occlusionmember 3615 is composed of a shape-memory metal which undergoes a shapechange at a specific temperature to create a fluid pathway.

The catheter assembly is connected to a pump which controls the flow offluid from said second inline chamber 3620 to said first inline chamber3610. In one embodiment, the pump is a syringe pump that engages apiston 3625 within and proximate the proximal end of the second inlinechamber 3620 which pushes the fluid from said second inline chamber 3620into said first inline chamber 3610 at a predefined rate. In oneembodiment, the pump is controlled by a microprocessor. In oneembodiment, the microprocessor receives optional information fromsensors in the catheter or in the tissue to control the flow of thefluid from chamber 3620 into chamber 3610. In various embodiments, thefluid is heated in chamber 3610 using any conventional methods ofheating, including those discussed above. In various embodiments, thefirst inline chamber 3610 has more than one channel for the flow of thefluid to increase the surface area of contact of the fluid with thechamber 3610 surfaces, improving the efficiency of heating the fluid. Inone embodiment, the first inline chamber 3610 is optionally covered by amaterial that is a poor thermal conductor, preventing the escape of heatfrom the chamber 3610. This embodiment is preferred if the method ofheating is electromagnetic induction. In one embodiment, referring toFIG. 36B, the catheter 3605 includes an optional handle 3630 allowingfor safe maneuvering of the catheter assembly. In one embodiment, thehandle 3630 is composed of a material that is a poor thermal conductorto prevent thermal injury to the operator from over-heating of thecatheter 3605.

It is desirable to have an integrated system as it eliminates anyconnections that may malfunction or leak causing system malfunctionand/or injury to a patient or an operator. Additionally, it is desirableto have the fluid and heating chambers included as parts of the catheterassembly which eliminates problems encountered with corrosion of themetal in the heating chamber with multiple uses and also ensuressterility of the ablation fluid with multiple uses.

FIG. 36C illustrates the catheter assembly of FIG. 36B connected to agenerator 3640 having a heating element 3650 and a pump 3645, inaccordance with one embodiment of the present specification. Thecatheter connects to the generator 3640 with the heating element 3650and pump 3645. In various embodiments, the heating element 3650 is aresistive heater, an RF heater, a microwave heater, or anelectromagnetic heater. The piston 3625 engages with the pump 3645. Oninitiating therapy, the pump 3645 pushes on the piston 3625 to deliverfluid from the second inline chamber 3620 into the first inline chamber3610, opening occlusion member 3615 and delivering fluid at apredetermined rate. In one embodiment, the fluid is water. The water isheated in the first inline chamber 3610 to be converted into vapor. Asthe vapor expands it is pushed out through the distal end of thecatheter 3605 to be delivered to the desired tissue for ablation. Thecatheter 3605 includes at least one delivery port 3606 at its distal endfor the delivery of vapor. In the pictured embodiment, the catheterassembly includes a handle 3630 for manipulating the catheter 3605 whichhas been filled with heated water vapor.

FIG. 36D illustrates a catheter assembly 3660 having an inline chamber3662 for heat transfer in accordance with another embodiment of thepresent specification. The catheter assembly 3660 includes a catheter3661 having an elongate body with a distal end, a proximal end, and alumen within. An inline heating chamber 3662, having an elongate body, adistal end, a proximal end, and a lumen within, is attached via itsdistal end to the proximal end of the catheter 3661. In variousembodiments, the heating chamber comprises a Curie point material, asfurther described below. In one embodiment, the Curie point material isin the form of a metal slug. A filter and one-way valve 3663, having adistal end and a proximal end, is attached via its distal end to theproximal end of the inline heating chamber 3662. In the picturedembodiment, the filter and one-way valve 3663 are separate from theheating chamber 3662. In another embodiment (not shown), the heatingchamber is shaped into a filter media, serving a dual purpose as heatingchamber and filter/valve, and a filter and one-way valve is notincluded. A pump 3664 is attached to the proximal end of the filter andone-way valve 3663. In one embodiment, the pump 3664 is a syringe pump.During operation, electrical energy is supplied to an induction coilwrapped about the heating chamber 3662. Magnetic fields created by thecoil induce heat production within the heating chamber, as described ingreater detail below, to cause water pumped into the heating chamber bythe attached pump to convert into steam for ablation.

FIG. 36E illustrates a catheter assembly 3600 connected to a heatingcomponent 3670 in accordance with one embodiment of the presentspecification. The catheter assembly 3600 is similar to that describedwith reference to FIGS. 36A and 36B and includes a catheter 3605, afirst inline chamber 3610 for heating water, an occlusion member 3615, asecond inline chamber for storing water, a piston 3625, and a handle3630. The heating component 3670 comprises a generator box 3672, an RFcoil 3674, a pump 3676, and an opening/attachment point 3678 for thecatheter assembly 3600. In one embodiment, the pump 3676 is a syringepump.

The proximal end of the catheter assembly 3600 slides into the catheterattachment opening 3678 and the piston 3625 engages with the pump 3676and the first inline chamber 3610 slides through the generator box 3672and becomes centered in the coil 3674. In various embodiments, the firstinline chamber 3610 comprises a ferromagnetic (FM) or curie-point metal.Upon initiation of therapy, the RF coil 3674 heats the first inlinechamber 3610 while the pump 3676 pushes water or saline through theocclusion member 3615 from the second inline chamber 3620 into the firstinline chamber 3610. The water is vaporized in the first inline chamber3610 and the resultant vapor is pushed through the catheter 3605 lumenon to the tissue to be ablated. In one embodiment, the action of thepump controls the amount of vapor generated. In various embodiments, theheating component 3670 is positioned vertically, as pictured, so thatany condensate flows back into the heated ferromagnetic chamber 3610.

In various embodiments, the temperature of the first inline(ferromagnetic) chamber is determined by the heat losses from thecatheter body. The temperature of the ferromagnetic chamber and flow ofthe water are both controlled through feedback from an optionaltemperature sensor proximate the tip of catheter. Optional temperaturesensors are deployed to measure the temperature of the ferromagneticchamber and the temperature of the vapor exiting from the chamber.Additional optional sensors monitor the catheter body temperature andwarn the operator of high catheter body temperatures. In one embodiment,the catheter includes a first sensor which communicates with a secondsensor in the heating component to adjust vapor generation parametersbased on the type of catheter being used. In one embodiment, thediameter of the lumen of the catheter gradually decreases toward thedistal end of the catheter. In another embodiment, the inner diameter ofthe distal end of the catheter is different from the inner diameter ofthe proximal end of the catheter, resulting in a differential pressurealong the length of the catheter. In another embodiment, the firstinline chamber includes an outer coating which allows for the conductionof electromagnetic energy but is resistant to the transmission of heatfrom inside the chamber to outside the chamber or to the coil.

In various embodiments, the ablation system further includes a mechanismto prevent premature removal of the catheter to avoid operator injuryfrom the heated ferromagnetic chamber. The safe temperature for removalof the catheter assembly from the generator box is less than 50° C. Inone embodiment, the mechanism includes a shape memory metal which, whenheated above 50° C., actuates a latch preventing release of the catheterassembly from the generator box. As the temperature drops below 50° C.,the latch retracts and the catheter assembly can be released. In anotherembodiment, the mechanism is a locking mechanism controlled by themicroprocessor which unlocks when a safe temperature is reached. In yetanother embodiment, the mechanism is a warning light or sound controlledby the microprocessor which changes color or tone respectively, when asafe temperature is reached.

In various embodiments, the catheter of the catheter assemblies of thevapor ablations systems of the present specification has two layers. Thecatheter includes an elongate body with a lumen within, a proximal end,and a distal end. The proximal end is in fluid communication with thevapor generating components of the system and the distal end includesone or more openings for the delivery of vapor. The catheter includes aninner layer and an outer layer. In one embodiment, the inner layer is athermally conducting layer and the outer layer is a thermally insulatinglayer. The thermally conducting inner layer is in thermal contact withthe heating mechanism of the vapor generation system to heat the lumenof the catheter to prevent premature condensation. In variousembodiments, the inner layer is movable independently from and relativeto the outer layer. In one embodiment, the inner layer is made ofcopper. In one embodiment, the outer layer is made of PEEK. Optionally,in various embodiments, a third layer is formed between the inner andouter layers. The third layer is an insulating layer and, in variousembodiments, comprises a layer of air or a vacuum. In one embodiment,the catheter has a length of approximately 230 cm. In one embodiment,the inner layer has an inner diameter of approximately 1.0 mm and anouter diameter of approximately 1.4 mm and the outer layer has an innerdiameter of approximately 1.5 mm and an outer diameter of approximately2.5 mm. In one embodiment, both the inner and outer layers are comprisedof PEEK. In one embodiment, the catheter further includes a coveringsheath over its proximal end. In one embodiment, the sheath has a lengthof approximately 50 cm, an inner diameter of approximately 2.6 mm, andan outer diameter of approximately 3.5 mm. In various embodiments, thesheath is comprised of plastic, acetal polyoxymethylene (POM), or PEEK.As stated above, it is desirable to have a large surface area within theheating chamber for contact heating of the ablative agent. This isaccomplished by having multiple small channels within the heatingchamber. In various embodiments, the channels are created by packing thechamber with metal tubes, metal beads, or metal filings, all of whichsignificantly increase the surface area for contact heating. FIG. 37Aillustrates a heating chamber 3705 packed with metal tubes 3707 inaccordance with one embodiment of the present specification. FIG. 37Billustrates a heating chamber 3715 packed with metal beads 3717 inaccordance with one embodiment of the present specification. FIG. 37Cillustrates a heating chamber 3725 packed with metal filings 3727 inaccordance with one embodiment of the present specification. In variousembodiments, the heating chamber 3705, 3715, 3725 and its channels 3707,3717, 3727 are made of a ferromagnetic material or a thermallyconducting material and the ablative agent 3708, 3718, 3728 flowsthrough these channels 3707, 3717, 3727 where it is heated rapidly andin an efficient manner.

In one embodiment, the heat chamber and its channels are made of amaterial having a specific Curie point or Curie temperature (T_(c)).These materials cease to be ferromagnetic when heated above their T_(c).If such a material is inside an electromagnet that is driven withalternating current, while the material is ferromagnetic below the Curietemperature T_(c), the magnetization of the material due to anexternally applied magnetic field causes the material to exhibit thetypical ferromagnetic hysteresis known in the art as the current in afield coil alternates through its cycles. As the applied magnetic fieldchanges, the magnetic domains inside the ferromagnetic material changedirection to align themselves with the applied field. The changing(flips) of these domains requires energy that is extracted from theapplied field and is converted to heat during the flipping of thedomains. The heat generation inside the ferromagnetic material increaseswith the area swept by the magnetic hysteresis (materials with a largerarea swept by the magnetic hysteresis are considered magneticallysofter) and by the rate of flips, which increases with the frequency ofthe applied alternating current. For example, if the ferromagneticmaterial is subjected to a magnetic field of several kHz, theferromagnetic material exhibits large magnetic hysteresis losses whileit is ferromagnetic below T_(c), which results in Joule heating. AtT_(c), the material abruptly loses its soft magnetic property, itsmagnetic hysteresis vanishes and the Joule heating is reduced by severalorders of magnitude. As a result, the material absorbs less energy formthe applied magnetic field and less Joule heating is generated in thematerial. If the heat dissipation is larger than the heat generation,then the material cools below T_(c), the hysteresis re-appears and itslosses increase again, heating resumes and the cycle is repeated.

This physical phenomenon is used to develop a heating device with anintrinsic and volumetrically distributed “thermostat”. In essence, suchan element absorbs the energy from the electromagnetic field preciselyas needed and where needed to maintain its temperature at T_(c) but willnot heat substantially above it, making it inherently failsafe fromoverheating. Moreover, areas of the device that are cooled due to heattransfer to any surrounding media, such as water or steam, immediatelyreheat while areas where heat has not been transferred to the mediacease heating.

T_(c) can easily be adjusted by selecting the ratios of low-cost basemetals in the material alloy. Industry standard soft magneticnickel-iron alloys containing from about 28% to 70% nickel (Ni), withthe balance substantially iron, have Curie temperatures ranging fromroom temperature to 600° C. For target temperatures of 100° C.-120° C.,the class of low-nickel alloys containing 30% Ni are most suitable. Forhigher temperatures, higher Ni concentrations are desirable. Smalladditions of copper (Cu), silicon (Si), manganese (Mn), or chromium (Cr)allow for alloying of very precise Curie temperatures. For example,several low Curie temperature iron-chromium-nickel-manganese(Fe—Cr—Ni—Mn) alloys are listed in Table 3 below.

TABLE 3 Chemical Composition [wt. %] T_(c) [° C.] Cr4Ni32Fe62Mn1.5Si0.555 Cr4Ni33Fe62.5Si0.5 120 Cr10Ni33Fe53.5Mn3Si0.5 10 Cr11Ni35Fe53.5Si0.566 Ni37Fe62Traces1 250 Ni77Fe14Cu5Mo4 400

Referring to Table 3, an alloy having a composition ofCr4Ni32Fe62Mn1.5Si0.5 has a Curie temperature of 55° C., an alloy with acomposition of Cr4Ni33Fe62.5Si0.5 has a Curie temperature of 120° C., analloy with a composition of Cr10Ni33Fe53.5Mn3Si0.5 has a Curietemperature of 10° C., and an alloy with a composition ofCr11Ni35Fe53.5Si0.5 has a Curie temperature of 66° C.

In various embodiments, other Curie materials with higher Curietemperatures may also be used. For example, referring to Table 3,Permenorm® 3601K5, having a composition of 37% Ni, 62% Fe, and 1% tracesand a Curie temperature of 250° C., is used in one embodiment. Inanother embodiment, MuMetal®, having a composition of 77% Ni, 14% Fe, 5%Cu, and 4% Mo and a Curie temperature of 400° C., is used as a Curiematerial.

FIG. 37D is a graph illustrating Curie temperature (T_(c)) as a functionof nickel content as described in Special-Purpose Nickel Alloys, ASMSpecialty Handbook: Nickel, Cobalt, and Their Alloys, Dietrich, et al.,ASM International, 2000, p 92-105, FIG. 4. As can be seen in the graph,the Curie temperature range 3702 of a material can be adjusted betweenroom temperature and 600° C. by varying the nickel content of thematerial to between approximately 30 to 75% nickel.

Incorporating a heating chamber comprised of a Curie point material, asdescribed above, provides a vapor ablation system that utilizes the fullextent of steam as an ablative agent in a safe and responsive fashion.The system is safe because the steam cannot be heated to a temperaturehigher than the Curie temperature of the material being used, thereforeminimizing the risk of burns to the user. For example, in oneembodiment, an ablation system includes a heating chamber comprised of aCurie point material with a Curie temperature of 130 degrees Celsius.The Curie point material is a ferromagnetic material from roomtemperature up to the Curie temperature of 130 degrees Celsius. Oncethis material is heated to its Curie point (130° C.), it ceases to beferromagnetic and heating due to magnetic hysteresis loss ceases. Theheating chamber is placed in an induction coil and the induction coil isenergized with high frequency electrical energy. In various embodiments,the energy is either AC power or RF energy. In one embodiment, theenergy is equal to 20 kHz. The high frequency energy causes the Curiepoint material to flip its magnetic domains very quickly to align withthe externally applied field. As the current applied to the inductioncoil is increased during one cycle of the alternating current, themagnetic field increases and the magnetization of the Curie materialincreases. As the magnetic field is increased, magnetization approachesand reaches saturation where the magnetization does not increase eventhough the applied magnetic field may increase. The current is thenslowly reduced from the maximum applied current to zero. As the currentis reduced, the magnetic field decreases and the Curie materialundergoes the magnetic hysteresis known in the art, meaning as thecurrent is reduced to zero, there remains magnetization in the materialeven though the magnetic field has vanished. The current then reversespolarity and the generated field reverses polarity as well. The appliedfield now reduces the remnant magnetization of the Curie material,reduces it to zero and then increases magnetization in the oppositedirection. This current is continuously applied and increased to achievenegative magnetization saturation. The current is then reduced again tozero, during which the material undergoes the negative branch of thehysteresis loop. The above process is repeated very quickly, such as, inone embodiment, 20,000 times per second. During this process, theapplied magnetic field causes the magnetic domains on the atomic scaleto flip, generating heat in the material. This heat is consideredelectrical loss in the material and is used to heat the water coming incontact with the Curie point material in the ablation system and convertthe water to steam. Any concurrent eddy current losses are small incomparison. The process continues to occur as long as the material isbelow the Curie point and thus ferromagnetic. Once the temperature ofthe material is increased above the Curie point, hysteresis collapses,the material ceases to be ferromagnetic and Joule heating due toferromagnetism ceases. The material cools below the Curie point and thencan be heated again by the above process but will never increasesubstantially above the Curie temperature.

Water is passed through the heating chamber having a Curie pointmaterial with a Curie temperature of 130° C. As the material temperaturerises to 100° C., the water is converted to vapor by the heat generatedby the process described above. Water enters one side of theflow-through heating chamber, turns to steam, and exits the other sideof the heating chamber as vapor. In various embodiments, the temperatureof the water as it enters the chamber is slightly lower than its boilingpoint, for example, 90-95° C. In one embodiment, the temperature of thewater as it enters the chamber is room temperature. The benefit providedby the Curie point material is that the material will not heatsubstantially above its Curie point temperature, regardless of how muchpower is applied to the induction coil. Therefore, in the describedembodiment, the steam is only heated to 130° C. and can never besubstantially higher than this temperature. Using a Curie point materialconfers a built-in safety mechanism so the user and/or patient will notbe burned by excessively heated vapor. The Curie point material acts asif it includes built-in and volumetrically distributed heat sensors,providing a closed feedback loop and preventing the material from risingabove a specific temperature. A non-Curie point material will heat to ahigher temperature and therefore the converted steam will also have ahigher temperature, creating a significant burn risk for the user andpatient. Another benefit provided by using a Curie point material isthat it creates a steam ablation system that is consistently responsive.The intrinsic thermostatic properties of the Curie point materialsproduce a heating gradient. In the example above, the user can beconfident that the system will always produce vapor that will be between100 and 130° C. The use of a non-Curie material for the heating chamberresults in a system in which the temperature of the generated steam isnot easily controlled. A heating chamber comprised of a non-Curie pointmaterial would require temperature sensors so the user would know whento cease application of current. A non-Curie point material wouldeventually melt if the current were to be continuously applied and thematerial's Curie point is above its melting point. In some embodiments,the Curie point temperature could be as high as 300° C. based on thedesired application or construction of the heating chamber or the amountof vapor needed for the desired therapeutic effect.

Use of a Curie point material in the heating chamber also provides avapor ablation system that is inherently energy saving and cannot beexhausted. In other words, continued use of such a heating chamber willnot cause the material to lose its Curie point properties. Once theCurie point material reaches its Curie temperature, it ceases to absorbthe electrical energy supplied. The material absorbs only as much energyas it needs to reach the Curie temperature, therefore there is no excessdraw of power. The system is scalable in terms of quantity of Curiepoint material. In various embodiments, the amount of Curie materialused to generate steam varies from millimeters in size to tons ofmaterial.

Another benefit provided by the Curie point material heating chamber isthat the impedance of the induction coil will change with the heat load.This is due to the fact that the Curie point material acts as the corematerial of an inductor coil whose magnetic properties determine theinductance and thus the impedance of the coil. This will be used as asensing mechanism to precisely control the power delivered to the coiland thus to the heating chamber. The presence or absence of water at theheating chamber can instantaneously be determined and used for precisepurging of entrapped air.

The use of steam as an ablative agent provides further benefits. Steamdoes not leave any harmful residues in the tissue, it simply returns towater. In addition, the steam does not create excessive gas volumes butis rather reduced in volume 600 times through condensation. Steam as anablative agent also delivers its energy to a highly predictable depthwithout harming healthy tissue beneath.

Referring again to FIG. 37B, in one embodiment, a heating chamber 3715is packed with metal beads, or ball bearing balls 3717, comprised of aCurie point material. The heating chamber 3715 is packed tightly withthe ball bearing balls 3717. An ablative agent 3718, for example in theform of water, is passed through the heating chamber 3715 and over theball bearings 3717. The tight packing of the ball bearings 3717 withinthe chamber 3715 provides a very large overall surface area for contactof the Curie point material with the ablative agent 3718. Through theinduction process described above, the ball bearings 3717 generate heatand convert the water into steam. In one embodiment, the heating chamberis heated uniformly. In one embodiment, the heating chamber comprises acylindrical tube with a proximal end and a distal end. The tube isfilled with the Curie-point material ball bearing balls. The tubeexperiences less heat loss at its distal end as the ablative agent exitsthe heating chamber as vapor. In one embodiment, optional temperaturesensors are added along the heating chamber to provide temperaturefeedback and fine-tuning of the application of current to the heatingchamber based on said feedback.

In various embodiments, the system includes a microcontroller orcomputer and the electrical current supplied to the induction coil andthus to the Curie point material filled heating chamber is controlled bysaid computer or microcontroller. In various embodiments, the computeror microcontroller is pre-programmed to control the system to generate aspecific amount of steam at a pre-determined temperature. In otherembodiments, the current is not controlled by a computer ormicrocontroller and no programming is provided. In one embodiment, thesystem further includes at least one temperature sensor as describedabove. In one embodiment, the system further includes at least onepressure sensor. Feedback from said temperature and/or pressure sensorsis used by the microcontroller or computer to regulate steam dosing anddelivery. In one embodiment, the system further includes a userinterface for input of vapor delivery parameters and monitoring ofsystem status in real-time. In one embodiment, all components of thesystem are thermally insulated such that surface temperatures do notexceed more than 5° C. above ambient temperature. In another embodiment,the temperature of any external surface that has the potential for humancontact is maintained below 60° C. Vapor is delivered rapidly andon-demand.

The vapor ablation systems of the present specification having Curiepoint materials to heat an ablative agent operate via a set of technicalparameters in order to provide the physician with a specific set of enduser parameters. In other words, for example, one embodiment of a vaporablation system includes a catheter having a heating chamber wherein theheating chamber is filled with Curie point material ball bearing ballsand the catheter and heating chambers each have specific lengths. TheCurie temperature of the ball bearing balls is 130° C. and water isintroduced into the system at a temperature of 95° C. An induction coilaround the heating chamber is supplied with 20 kHz of electrical energy.The lengths of the catheter and heating chamber, the Curie temperatureof the material, starting temperature of the water, and amount of energysupplied to the induction coil are all technical parameters of thesystem. When in operation, the system generates steam having a specifictemperature, for example between 100 and 130° C., at a specific rate.The temperature of the steam and rate of its delivery are end userparameters dictated by the technical parameters. One of ordinary skillin the art would realize that many technical parameters and userparameters, and combinations thereof, are possible for such a system andthe examples given above are not intended to be limiting.

In various embodiments, materials having different Curie temperaturescan be created by modifying the elemental composition of said materials,as shown in Table 3 above. In some embodiments, vapor ablation systemsof the present specification include Curie point materials having aCurie temperature ranging from 60 to 500° C., more preferably 100 to400° C., even more preferably 150 to 300° C., and most preferably 250 to280° C. The Curie temperature of the material should be low enough tominimize the risk of burns from exposure to the heated steam while alsohigh enough to account for heat loss in the catheter of the ablationsystem to overcome condensation inside the catheter. Ideally, steamexiting the distal, or operational, end of the catheter should have atemperature between 98 and 120° C. at pressures between 1 and 2 atm. Invarious embodiments, the pressure of operation is less than 1 atm. Inother embodiments, the pressure of operation is greater than 2 atm butless than 10 atm. As is known in the art, the boiling point of watervaries depending on elevation and atmospheric pressure and suchdifferences can be accounted for by changing the technical parameters ofthe system. Therefore, in various embodiments, the length of thecatheter is considered when determining the Curie temperature of thematerial to be used. In various embodiments, catheters having a lengthof less than 6 feet are used with the ablation system. In otherembodiments, catheters having a length of 6 feet and greater are used. Alonger catheter will require a heating chamber having a higher Curietemperature to account for heat loss experienced by the steam as ittravels distally through the catheter. Since the Curie temperature of aCurie point material is fixed and cannot be changed, each material willhave a maximum possible temperature corresponding to its Curietemperature. As such, the steam generated can never have a highertemperature than the Curie temperature of the material used for heating.However, a Curie point material can have a temperature that is lowerthan its Curie temperature and this is controlled by the amount ofelectrical energy supplied to the induction coil. By adjusting theamount of energy supplied to the induction coil, a user can control thetemperature of the ablative agent exiting the catheter, preferablywithin a range between 100° C. and the Curie temperature of the materialto ensure steam generation. Therefore, in one embodiment, a vaporablation system includes a Curie point material having a high enoughCurie temperature to ensure delivery of steam from the distal end of anylength of catheter common in the art. Since the temperature of thematerial can be reduced to anything lower than the Curie temperature ofthe material, the physician can use the same heating chamber to deliversteam through catheters of considerably shorter length or lowertemperature.

In some embodiments, the heating chamber containing the Curie pointmaterial is a single use, disposable component of the system. The Curiepoint material comes into contact with water during a procedure,becoming non-sterile and precluding its use in subsequent procedures.Additionally, exposure of the metal to the fluid or its content couldproduce chemical byproducts with repeat use which could be harmful to apatient and may preclude repeat use of the heating element for medicalapplications. In another embodiment, the Curie point material iscontained within a clam-shell shaped heating chamber similar to thatdescribed in FIGS. 31A and 31B. In this embodiment, the Curie pointmaterial does not come into physical contact with the water but insteadtransfers its generated heat to the water through the walls of theclam-shaped heating chamber. In one embodiment, the Curie point materialfilled, clam-shaped heating chamber is reusable. In one embodiment, theCurie point material filled, clam-shaped heating chamber is comprised ofPEEK, a plastic of high impact strength, so that it will withstand adrop onto a concrete floor. In one embodiment, the outer surface of theclam-shell shaped heating chamber is insulated. In various embodiments,the Curie point materials used in the vapor ablation systems of thepresent specification include a nickel/iron alloy comprising at least25% nickel.

The use of the vapor ablation systems of the current specification whichinclude a Curie point material heating chamber provides sterilelow-cost, disposable catheters to avoid the risk of infection in amedical operating environment. This necessitates that costly parts, suchas the induction heater, must be reusable and ideally not be in contactwith the sterile inside of the catheter. With conventional conductionheaters, this requirement would make it difficult to facilitate optimalheat transfer to the water for evaporation through the channel walls.However, placing a low-cost heating element inside the water channel indirect contact with the flowing water provides efficiency in vaporizingwater through heat conduction.

FIG. 37E is an illustration of one embodiment of a vapor ablation system3700 with a Curie point material induction heating chamber 3709. Fluid3701 from a sterile IV bag is pumped into an intermediary storage vessel3703 where the solution is pre-heated to approximately 95° C.Pre-heating the water reduces the energy demand for steam generation toessentially the latent heat of water vaporization. A preciselycontrollable dosing pump 3705, of a positive displacement type in oneembodiment, delivers exact amounts of water on demand into the catheter3707 channel. With a low dead volume on the discharge side of the dosingpump 3705, the water immediately enters the heating chamber 3709, whichhas been energized shortly before. An induction coil 3711, connected toa flash heater with control electronics 3713, is wrapped about theheating chamber 3709 and provides energy to the heating chamber 3709. Inone embodiment, the heating chamber 3709 is tightly packed with Curiepoint material ball bearing balls having a Curie temperature of 150° C.Fine pores 3715 are present about the ball bearings. The water is forcedthrough the fine pores 3715 of the heating chamber 3709, assuring thatall water contacts the metal surface and exits entirely as steam 3717.The described system is not susceptible to air bubbles or vapor lock.The heating chamber 3709 also acts as a filter and, in one embodiment,includes at least one pressure sensor 3710 to monitor the supplypressure to the catheter (back-pressure of the system during flow),providing crucial information regarding proper system operation. Too lowpressure indicates a leak while excessive pressure signals anobstruction in the catheter. In one embodiment, a sudden rise ordecrease in pressure will cause an attached microcontroller to initiatea failsafe shutdown. Therefore, in various embodiments, the heatingchamber 3709 serves a triple purpose as filter, heater, and high-surfacearea heat exchanger.

Optionally, in one embodiment, the system 3700 includes an air pump 3719to inflate and deflate at least one optional positioning balloon 3721 atthe distal tip of the catheter 3707. The pump 3719 will inflate theballoon to a preset pressure to create a vapor seal inside a body cavityand functions similarly to the positioning attachment 22 depicted inFIG. 2D. A microprocessor will then calculate the dimensions (diameteror volume) of the organ to be ablated. The air pump 3719 suppliespressure to the balloon 3721 through a separate air port 3723.

In various embodiments, the system includes resistors and/or valvesalong the path of the vapor to further increase the pressure, in turnincreasing the temperature of the vapor according to Gay-Lussac's law.Raising the pressure of the vapor to 20 PSIG increases the boiling pointof the water to approximately 125° C.

FIG. 37F is an illustration of another embodiment of a vapor ablationsystem 3730 with a Curie point material induction heating chamber 3739including a user interface 3741. The physician interfaces with a consolethrough a touch screen user interface 3741 to set treatment parameters.During operation, the physician may also use optional multi-functionfoot switches 3743 for hands-free control. A microcontroller 3745processes sensor inputs in real-time and tightly controls the water pump3735, optional air pump 3749, and heating chamber 3739 through closedfeedback loops. At all times, a fault detection routine monitors propersystem operation and immediately shuts the system down if triggered byparameters being detected to be outside the safe operating range.Warnings, such as low water supply, abnormal temperatures and pressures,and system default, will be issued audio-visually according toselectable criteria pre-set by the physician. The alarms are issued wheninformation from any of the sensors falls outside of a predeterminedvalue range. All sensor and control parameters will be logged with timestamps for later review of the procedure.

The amount of control of the Curie point material induction heatingchamber 3739 will be increased by monitoring the coil impedance “seen”by an impedance tuner circuit 3746 which changes with changing heatload. While the impedance tuner 3746 will continuously attempt to matchthe output impedance of an RF driver 3748 stage to the input impedanceof the induction coil, the degree of mismatch is a direct measure of theelectrical load inside the coil. This electrical load in turn is adirect measure of the heat load. The impedance tuner 3746 communicatesthis mismatch to the microcontroller 3745 as input for process control.Together with the Curie point “thermostat” of the heating chamber 3739,this monitoring will provide increased control and responsiveness of thesteam generation.

Optionally, in various embodiments, temperature and pressure sensors3747 are installed in discharge lines of the air and water pumps.Together with pump drive parameters (particularly with positivedisplacement pumps), the mass flow of water and air can be determined. Apositive displacement pump includes a reliable correlation between pumpshaft revolutions and the pumped volume of fluid (gas or liquid). Bymeasuring the pressure and temperature, the mass flow can be derivedaccurately. Controlling the mass flow of a fluid, either liquid or gas,yields a more meaningful parameter for process control because volume istemperature dependent and must be temperature-compensated. Deriving themass flow mathematically from existing sensors 3747 eliminates the needfor costly mass flow sensors.

In one embodiment, the water pre-heater 3733 includes a conventionalresistance heater element and uses a proportional-integral-derivativecontroller (PID controller) for rapid heat-up without significanttemperature overshoot. In one embodiment, the water pre-heater 3733pre-heats the water to approximately 95° C., similarly to the systemdescribed above with reference to FIG. 37F. In another embodiment, thesystem does not include a water pre-heater and water is injected intothe induction heating chamber 3739 at room temperature.

In one embodiment, the amount of steam generated by the vapor ablationsystems having Curie point material heating chambers is selectablewithin a range of 15 to 150 ml/sec. In one embodiment, the touchscreenuser interface allows intuitive, quick adjustment of parametersincluding power, steam flow, and pressure. In one embodiment, a syringepump is used to control the fluid flow to the heating element. In oneembodiment, the volume of the syringe pump is at least 60 ml. In oneembodiment, the system includes a self-test feature to ensure properfunction. In one embodiment, the system uses a maximum of 700 to 1000Watts of power and requires only a standard 120 VAC/15 A outlet. In oneembodiment, the system is double-insulated, includes a grounding pad anduses a separation transformer to electrically isolate the entire systemfrom line voltage.

The above features of the vapor ablation systems allow a user toprecisely maintain steam temperature and meter selected steam volume ata constant flow rate. The systems provide rapid start and stop of steamdelivery and immediate shutdown after fault detection. In oneembodiment, the system includes an inherent failsafe with interlockfeature.

FIG. 37G is a flowchart illustrating the steps involved in oneembodiment of a method of generating steam using a vapor ablation systemhaving a Curie point material heating chamber. At step 3752, a Curiepoint material-filled heating chamber is positioned within an inductioncoil. The induction coil is energized with high frequency energy at step3754. The energized induction coil induces magnetic hysteresis andresultant heat generation within the heating chamber at step 3756. Then,at step 3758, water is injected into a proximal end of the heatingchamber. The water passes distally through the heating chamber and isconverted into steam via heat transfer within the heating chamber. Thesteam exits through a distal end of the heating chamber and passes intoan ablation catheter attached to said distal end of the heating chamberto be used for ablation at step 3760. At step 3762, the temperature ofthe heating chamber reaches the Curie temperature of the Curie pointmaterial. The heating chamber temporarily loses its ferromagneticproperties and ceases to absorb energy through hysteresis loss. At step3764, the temperature of the heating chamber decreases below the Curietemperature of the Curie point material as it is no longer absorbingenergy and generating heat. Once below the Curie temperature, theheating chamber regains its ferromagnetic properties, can once again beheated, and the process continues back at step 3756.

FIG. 37H is a flow chart illustrating the steps involved in tissueablation using various ablation systems of the present specification. Atstep 3770, water is pre-heated using DC power and the pre-heated wateris delivered to a heating element at a pre-determined rate (ml/min). Inone embodiment, the pre-heated water is at approximately 95° C. Inanother embodiment, the water is not pre-heated but rather roomtemperature water is provided to the heating element. At step 3772, theheating element heats and converts the water to steam. In oneembodiment, the heating element is a Curie point material heaterelement. RF energy is provided to an induction coil positioned about theheating element to resulting in heating of the heating element andconversion of the water to steam. In various embodiments, steamgenerated by the heating element and delivered to a catheter of theablation system is between 100 and 150° C. At step 3774, steam having atemperature of approximately 100° C. traveling through the catheterloses a small amount of its energy into the catheter wall while amajority of the steam is delivered into a body cavity. A small portionof the thermal energy of the steam heats the cavity itself while most ofthe thermal energy of the steam, now at approximately 98° C., istransferred to surface tissues surrounding the body cavity at step 3776.Then, at step 3778, the thermal energy causes tissue ablation in anablation layer of the surface tissues. Finally, at step 3779, the steam,having released its thermal energy, converts back to water. Theremaining energy during this conversion is dumped into bulk tissue whichacts as an infinitely large heat reservoir.

In order to have high insulation properties, the catheters describedabove require increased wall thickness. The increased wall thicknesswould decrease the size of the lumen and increase the resistance to flowof the ablative agent. Therefore, in various embodiments, the innersurface of the catheter includes a groove to decrease the resistance toflow of an ablative agent. FIG. 38A illustrates a cross-sectional viewof one embodiment of a catheter 3805 having an internal groove 3810 todecrease flow resistance and FIG. 38B illustrates an on-end view of oneembodiment of a catheter 3815 having an internal groove 3820 to decreaseflow resistance.

In another embodiment, the resistance to flow is reduced by sending asound wave down the catheter bore along with the ablative agent tocreate sympathetic resonances. The sympathetic resonances create achanneling effect where friction with the vessel wall is dramaticallyreduced.

To improve the thermal insulation property of the catheter, a duallayered catheter can be formed with a thin layer of air or insulatingfluid between the two catheter layers. In one embodiment, the insulatinglayer of air or fluid is circulated back into the power generator tofacilitate heat transfer into the generator rather than through thecatheter walls. FIG. 39A illustrates a cross-sectional view of a doublelayered catheter in accordance with one embodiment of the presentspecification. The catheter includes an inner wall 3905 and an outerwall 3915 separated by a thin layer 3910 of air or insulating fluid. Thetwo walls 3905, 3910 are connected at their proximal and distal ends(not shown). FIGS. 39B and 39C illustrate cross-sectional views of adouble layered catheter in accordance with another embodiment of thepresent specification. The catheter includes an inner wall 3925 and anouter wall 3935. The two walls 3925, 3935 are connected at theirproximal and distal ends (not shown) and are connected at intervals byspokes 3940 which provide additional support. Multiple air or fluidfilled channels 3930 are positioned between the two walls 3925, 3935. Inone embodiment, the inner and outer walls (and spokes shown in FIG. 39B)are composed of polyether ether ketone (PEEK).

FIG. 39D illustrates a dual layered catheter 3950 having the internalstructure depicted in FIG. 39B. The catheter 3950 includes an elongatebody with a proximal and a distal end. The proximal end includes a firstport 3951 for the input of an ablative agent, such as steam, and asecond port 3952 for the insufflation of a pair of inflatablepositioning attachments 3958 positioned proximate the distal end of thecatheter 3950. In one embodiment, a length of catheter 3950 positionedbetween said positioning attachments 3958 includes at least one opening3955 for the delivery of ablative agent. In one embodiment, the lengthof the catheter between said positioning attachments 3958 isapproximately 5 cm. In one embodiment, the catheter includes a thirdlayer 3954 about a portion of its proximal end. The third layer 3954functions as a handle and thermally insulates the user from theremaining layers of the catheter. In one embodiment, the third layer3954 has a length of approximately 50 cm. In one embodiment, the lengthof the catheter 3950 beyond the handle is equal to the length of anendoscope plus 2 cm. The catheter 3950 includes an outer layer 3956 andan inner layer 3957 separated by a plurality of spokes 3959. A pluralityof air or fluid filled spaces 3960 separates each spoke 3959 from oneanother and the outer layer 3956 from the inner layer 3957.

In one embodiment, the outer diameter d₁ of the outer layer 3956 isapproximately 2.5 mm and the inner diameter d₂ of the inner layer 3957is approximately 0.5 mm. The third layer 3954, or handle, includes anouter diameter d₃ of varying size as this portion of the catheter is notinserted into an endoscope during operation. In another embodiment, thecatheter includes only one spoke 3961 separating the inner layer 3956from the outer layer 3957 and a single air or fluid filled channel 3962fills the remaining space between the two layers. The “honeycomb”arrangement of the catheter depicted in FIGS. 39B through 39D providesthermal insulation and a more flexible structure as some cathetermaterial has been removed.

One advantage of a vapor delivery system utilizing a heating coil isthat the vapor is generated closer to the point of use. Traditionalvapor delivery systems often generate vapor close to or at the point inthe system where the liquid is stored. The vapor must then travelthrough a longer length of tubing, sometimes over 2 meters, beforereaching the point of use. As a result of the distance traveled, thesystem can sometimes deliver hot liquid as the vapor cools in the tubingfrom the ambient temperature.

The devices and methods of the present specification can be used tocause controlled focal or circumferential ablation of targeted tissue tovarying depth in a manner in which complete healing withre-epithelialization can occur. Additionally, the vapor could be used totreat/ablate benign and malignant tissue growths resulting indestruction, liquefaction and absorption of the ablated tissue. The doseand manner of treatment can be adjusted based on the type of tissue andthe depth of ablation needed. The ablation device can be used not onlyfor the treatment of Barrett's esophagus and esophageal dysplasia, flatcolon polyps, gastrointestinal bleeding lesions, endometrial ablation,pulmonary ablation, but also for the treatment of any mucosal,submucosal or circumferential lesion, such as inflammatory lesions,tumors, polyps and vascular lesions. The ablation device can also beused for the treatment of focal or circumferential mucosal or submucosallesions of any hollow organ or hollow body passage in the body. Thehollow organ can be one of gastrointestinal tract, pancreaticobiliarytract, genitourinary tract, respiratory tract or a vascular structuresuch as blood vessels. The ablation device can be placed endoscopically,radiologically, surgically or under direct visualization. In variousembodiments, wireless endoscopes or single fiber endoscopes can beincorporated as a part of the device. In another embodiment, magnetic orstereotactic navigation can be used to navigate the catheter to thedesired location. Radio-opaque or sonolucent material can beincorporated into the body of the catheter for radiologicallocalization. Ferro- or ferrimagnetic materials can be incorporated intothe catheter to help with magnetic navigation.

FIG. 40A is an illustration of a vapor ablation system 4000 usinginduction heating in accordance with one embodiment of the presentspecification. The vapor ablation system 4000 comprises a fluid circuitincluding a water reservoir 4002, a heating chamber 4004, and a catheter4010 connected by a contiguous fluid channel. In various embodiments,the contiguous fluid channel connecting the components of the fluidcircuit comprises flexible tubing having an internal lumen. In variousembodiments, one or more of the components of the fluid circuit aredisposable such that the separate components are discarded and replacedafter a single use or the entire fluid circuit is discarded after asingle use. In one embodiment, prior to use, a portion of the fluidchannel positioned between the water reservoir 4002 and the heatingchamber 4004 is blocked by a barrier, thereby blocking water frompassively flowing from the water reservoir 4002 to the heating chamber4004. In one embodiment, a check valve or a fracture diaphragm 4007 ispositioned in the contiguous fluid channel between the water reservoir4002 and the heating chamber 4004 to prevent water from entering theheating chamber 4004 until force is applied to the water to direct itinto the heating chamber 4004. During operation, the barrier, checkvalve, or fracture diaphragm 4007 is breached by an increase in waterpressure as water is acted upon by a pump or driving mechanism,permitting water to flow from the water reservoir 4002 to the heatingchamber 4004.

Water travels from the reservoir 4002 into the heating chamber 4004where it is converted to steam. The resulting steam travels into thecatheter 4010 and out its distal end as ablative agent. The only pathwayfor water and steam to travel is from the reservoir 4002, through theheating chamber 4004, and out the distal end of the catheter 4010. Invarious embodiments, there are no other inputs, ports, or openings forreceiving fluid from an external source into the fluid circuit. Invarious embodiments, there are no other outputs, ports, or openings, forreceiving or expelling fluid external to the fluid circuit. In variousembodiments, the water reservoir 4002 comprises a pliable bag, asyringe, or any three dimensional enclosure configured to contain apredetermined volume of water.

The heating chamber 4004 is configured to be positioned within aninduction coil 4005. In various embodiments, the heating chamber can becylindrical, cuboid, or any other shape. In some embodiments, theinduction coil 4005 comprises an induction chamber 4001 having acylindrical volume around which a plurality of coils are positioned anda lumen 4003 within configured to receive the heating chamber 4004. Inother embodiments, the induction coil 4005 comprises only the coilitself which is wrapped about the heating chamber 4004. The inductioncoil 4005 comprises a plurality of coils for receiving an electricalcurrent and generating a magnetic field which leads to induction heatingof a ferromagnetic portion of the heating chamber 4004, as described infurther detail with reference to FIGS. 42 and 43. In variousembodiments, the frequency of the electrical current provided to theinduction coil is in a range of 100 Hz-200 kHz, more preferably 1kHz-100 kHz, more preferably yet 10 kHz-50 kHz, and most preferably 25kHz-35 kHz. In various embodiments, the heating chamber 4004 isinsulated to prevent heat losses from the chamber and/or thermal injuryto an operator.

Water is directed from the reservoir 4002 into the heating chamber 4004via force applied by a pump, motor, or other mechanism. In variousembodiments, water is directed into the heating chamber 4004 by a pumpdriven by a motor as described further below. In other embodiments, thewater reservoir 4002 is elevated relative to the heating chamber 4004and water from the reservoir 4002 is gravity fed into the heatingchamber 4004. In other embodiments, the mechanism for delivering waterfrom the reservoir 4002 to the heating chamber 4004 comprises a bladdertank. In one embodiment, the bladder tank comprises a diaphragmseparating two compartments within one tank. A first compartmentcontains compressed air while the second compartment contains water. Thecompressed air pushes on the diaphragm, which forces water out of thesecond compartment and into a heating chamber. In another embodiment,the mechanism to deliver water from the reservoir 4002 to the heatingchamber 4004 comprises an occluded water tank. The occluded water tankfunctions similarly to a toothpaste tube wherein a portion of theoccluded water tank is compressible and is squeezed to force water outof the tank and into a heating chamber.

In various embodiments, fluid from the water reservoir 4002 is pumpedwith precise dosing into the heating chamber 4004. In one embodiment,the water reservoir 4002 is configured to contain 200 ml of water. Aprecisely controllable, positive displacement dosing pump 4006 deliversexact amounts of water on demand into the induction heater chamber 4004for vaporization. Induction heating is preferred because it permitsheating of an element inside a sterile catheter without comprisingsterility and does not require complex electrical feed-throughs. Inaddition, the catheter itself can be disposable and thereforemanufactured at a low cost. In one embodiment, the heating chamberincludes 4004 a metal core and is mounted vertically. In one embodiment,the metal is steel. Water is introduced at the bottom of the heatingchamber 4004 at an inlet port at its proximal end. As described furtherbelow, in one embodiment, the metal core is a smooth rod with a slightlysmaller outer diameter than the inner diameter of a tube coaxiallypositioned over the core. An induction coil 4005 is wrapped about thetube of the heating chamber 4004. The core and the tube comprise theheating chamber 4004. Water introduced into the heating chamber 4004passes through the space between the core and the tube. Therefore, allwater is forced into close proximity of the core, contacting the metalsurface, vaporizing and exiting the chamber entirely as steam as long assufficient heating power is provided for a given flow rate. Steamcreated within the heating chamber 4004 exits via an outlet port at itsdistal end.

The generated steam is delivered to a luer lock connector 4008 connectedto the input port of a catheter 4010. The catheter 4010 is designed suchthat all parts that come into direct contact with the steam are able towithstand temperatures in excess of 100° C., preventing melting andsubsequent leaks or obstructions. The catheter 4010 includes one or moreopenings at its distal end for the delivery of steam 4014 to targettissues. In various embodiments, the catheter 4010 includes one or morepositioning attachments 4016 proximate its distal end. In oneembodiment, the positioning attachments 4016 comprise inflatableballoons and the catheter 4010 further comprises an insufflation port4018 at its proximal end. An air pump 4020 connected to the insufflationport 4018 is used to inflate said balloons. In various embodiments, thepositioning attachments, or balloons 4016, are inflated using airthrough the air pump 4020 and then the air expands once steam isgenerated by the system 4000. In some embodiments, the one or moreballoons 4016 are first inflated to a positioning volume by the air pump4020 and are then further expanded to an occlusive volume as the air isheated by the delivery of steam, establishing a non-puncturing seal. Inone embodiment, the occlusive volume is less than 120% of thepositioning volume. In various embodiments, the one or more balloons4016 are comprised of silicone. The silicone is thermally insulating soheat generated from ablation in the area proximate the outside of theballoons 4016 will not transfer passively and expand the air inside theballoons 4016. Therefore, in some embodiments, the air used forinsufflation must be actively heated from inside the catheter into theballoons 4016 to accomplish the desired heat expansion. In variousembodiments, the catheter 4010 has a coaxial design such that heatenergy from the steam is transferred to the air used for insufflation asthey both travel along the catheter 4010. The coaxial design of thecatheter 4010 allows for heat losses along the catheter to be capturedand transferred to the air in the balloons 4016 to generate a treatmentresponsive seal. In other embodiments, the catheter 4010 includes acoaxial lumen for heating the air or the balloons 4016 include aconductive metal inside for conducting heat from vapors in the catheterto the air in the balloons 4016.

When heating air from 37° C. (body temperature) to 100° C., the air willexpand by approximately 20%. Therefore, in one embodiment, the one ormore balloons 4016 are inflated to approximately 75% using the air pump4020, allowing for the remainder of the volume expansion to beeffectuated by heat transfer from the steam. Since the steam is notbeing directed into the balloons 4016, pressure within the balloons 4016will not change significantly. The air used to inflate the one or moreballoons 4016 behaves like an ideal gas at temperatures below 400° C.,as depicted in FIG. 40B, and follows approximately the ideal gas lawbelow:

PV=nRT

where P is the absolute pressure of the gas, V is the volume of the gas,n is the amount of gas, R is the ideal gas constant, and T is theabsolute temperature of the gas expressed in degrees Kelvin (degreesC.+273). Referring to FIG. 40B, the air behaves less like an ideal gasas it is heated beyond approximately 400° C., where the curves for thedensity of ammonia 4015, nitrogen 4017, and helium 4019 become lesslinear at temperatures over 400° C. In various embodiments, the air usedto inflate the balloons is defined by at least three differenttemperatures: starting temperature (T_(start)); ideal temperature(T_(ideal)); and, maximum temperature (T_(max)). In various embodiments,T_(start) is equal to 25° C. (room temperature), T_(ideal) is less thanor equal to 75° C., and T_(max) is equal to 125° C. In variousembodiments, the volume expansion of the balloons relative to the volumeat T_(start) ranges from 2% to 40% at T_(max) and from 1% to 20% forT_(ideal). In various embodiments, the system has a maximum continuousoperating time of less than or equal to 5 minutes and an idealcontinuous operating time of less than or equal to 2 minutes. In variousembodiments, the balloons are configured to have a maximum diameterchange, or expansion, of less than or equal to 5 mm and an idealdiameter change, or expansion, of less than or equal to 3 mm. Differenttemperatures at a substantially fixed pressure provide a volume ratioequal to the temperature ratio. Therefore, in one embodiment having theoperating parameters listed above, heating the air from 25° C.(T_(start)) to 125° C. (T_(max)) provides a temperature increase of 100K (398K/298K) which translates to a volume expansion of less than orequal to 33%. In one embodiment having the operating parameters listedabove, heating the air from 25° C. (T_(start)) to 75° C. (T_(ideal))provides a temperature increase of 50 K (348K/298K) which translates toa volume expansion of less than or equal to 17%. In various embodiments,the balloons have a first positioning diameter when inflated by actionof an air pump and a second occlusion diameter when the pumped air isheated by the steam generated by the system, as listed in Table 4 below:

TABLE 4 Positioning Diameter Occlusion Diameter Percent Change in Volume18 mm 21 mm 36% 20 mm 23 mm 32% 22 mm 25 mm 29%

Referring to Table 4, a balloon having a positioning diameter of 18 mmexpands to have an occlusion diameter of 21 mm, a 36% increase, when theinsufflation air is heated by the nearby steam. A balloon having apositioning diameter of 20 mm expands to have an occlusion diameter of23 mm, a 32% increase, when the insufflation air is heated by the nearbysteam. A balloon having a positioning diameter of 22 mm expands to havean occlusion diameter of 25 mm, a 29% increase, when the insufflationair is heated by the nearby steam.

In another embodiment, further volume expansion of the balloon is notdesired and the volume of the balloons is kept constant by monitoringthe pressure in the balloon and allowing a portion of expanded air toescape the balloon to keep the pressure, and therefore volume, constant.

FIG. 40C is an illustration of one embodiment of a catheter 4040 for usewith the vapor ablation systems of the present specification. Thecatheter 4040 includes an elongate body 4041 with a proximal end and adistal end. In one embodiment, the catheter body 4041 includes an innerlumen 4042 and an outer lumen 4043. The inner lumen 4042 is separatedfrom the outer lumen 4043 by a thermally semi-permeable wall 4044 whichallows a portion of the thermal energy to pass from the inner lumen 4042to the outer lumen 4043. The catheter also includes at least onepositioning balloon at its distal end. In the embodiment depicted inFIG. 40C, the catheter 4040 includes two positioning balloons 4045, 4046at its distal end with a plurality of delivery ports 4047 located on thecatheter body 4041 between the two balloons 4045, 4046. The deliveryports 4047 are in fluid communication with the inner lumen 4042. Anablative agent 4048 is introduced into the inner lumen 4042 at theproximal end of the catheter 4040 and exits through the delivery ports4047 into a target tissue area for ablation. In one embodiment, theablative agent 4048 is steam. Air 4049 is introduced into the outerlumen 4043 at the proximal end of the catheter 4040 and exits throughinflation ports 4050 into the balloons 4045, 4046 to inflate saidballoons 4045, 4046. Along the length of the catheter body 4041, the air4049 in the outer lumen receives thermal energy 4051 through thethermally semi-permeable wall 4044 from the ablative agent 4048 beingdelivered. The thermal energy 4051 expands the air 4049, allowing forthe air 4049 in the positioning balloons 4045, 4046 to thermally expandor contract to get a variable seal as ablative agent 4048 is delivered.This functionality provides a loose balloon seal (contacting withoutsignificantly expanding an elastic hollow organ) during dimensionmeasurement (no ablative agent 4048 delivered) and a tighter balloonseal (contacting and sufficiently expanding an elastic hollow organ)during the delivery of ablative agent 4048. The seal loosens aftercessation of delivery of ablative agent 4048. In various embodiments,the expansion of the balloons as a result of thermal energy 4051expanding the air 4049 is less than 125% of the original inflated volumeto prevent tearing or perforation of the hollow organ. In variousembodiments, one or both of the balloons 4045, 4046 has a first volumefor sizing and a second volume for occlusion. The balloons 4045, 4046are inflated to the first volume for sizing and then to the secondvolume for occlusion during ablation wherein the change in size from thefirst volume to the second volume occurs by expansion of air due to heatwith the passage of steam, by further inflation of the balloons 4045,4046 being pumped with air, or by both mechanisms. In variousembodiments, a second diameter of the balloons 4045, 4046 at the secondvolume is no greater than 5 mm larger or no greater than 25% larger thana first diameter of the balloons 4045, 4046 at the first volume. In oneembodiment, thermal energy 4051 is also conducted through the walls ofthe delivery ports 4047 and into the outer lumen 4043 as the deliveryports 4047 extend from the inner lumen 4042 to the exterior of thecatheter 4040. In one embodiment, the delivery ports 4047 are comprisedof metal for improved thermal conductivity.

FIG. 40D is a flowchart listing the steps of a method of using theablation catheter of FIG. 40C, in accordance with one embodiment of thepresent specification. At step 4055, the catheter is inserted into apatient's hollow organ and the distal end is positioned proximate thetissue to be ablated. The balloons are then inflated to a first volumeat step 4056 and the dimensions of the hollow organ are measured. Theablative agent is then delivered to ablate the tissue at step 4057. Thedelivery of the ablative agent also acts to expand the air being used toinflate the balloons, which causes the balloons to expand to a secondvolume greater than the first volume for a tighter seal. In variousembodiments, the second volume is less than 125% of the first volume. Atstep 4058, delivery of the ablative agent is stopped, allowing the airin the balloons to cool and the balloons to return to the first volume.

FIG. 40E is a flowchart listing the steps of a method of using theablation catheter of FIG. 40C, in accordance with another embodiment ofthe present specification. At step 4060, the catheter is inserted into apatient's hollow organ and the distal end is positioned proximate thetissue to be ablated. The balloons are then inflated to a first pressureat step 4061 and the dimensions of the hollow organ are measured. Theablative agent is then delivered to ablate the tissue at step 4062. Thedelivery of the ablative agent also acts to expand the air being used toinflate the balloons, which causes the balloons to expand to a secondpressure greater than the first pressure for a tighter seal. In variousembodiments, the second pressure is less than 125% of the firstpressure. At step 4063, delivery of the ablative agent is stopped,allowing the air in the balloons to cool and the balloons to return tothe first pressure.

It should be appreciated that an inflatable element, such as theballoons described with reference to FIG. 40C, can be used inconjunction with any of the vapor delivery systems and cathetersdescribed in the present specification. In various embodiments, aninflatable element, such as an inflatable balloon, positioned at orproximate a distal end of a catheter for use with a vapor delivery andablation system, includes a balloon sizing system which can be used forfirst sizing and then sealing a body cavity. Operationally, the catheterwith the balloon is inserted into a body cavity and the balloon isinflated to a first volume wherein a first characteristic pressure levelindicates that the balloon walls are touching the cavity walls. Thevolume at which the balloon walls contact the cavity walls providessizing information. Once the sizing information is obtained, the balloonis then increased to a second volume level wherein a secondcharacteristic pressure level indicates that the balloon walls aretouching the cavity walls with sufficient pressure to create a seal.This volume level is dynamically managed because the pressure willchange over the course of treatment (the steam will cause the volume topartially increase on its own). Once the treatment is done, the balloonis deflated and the catheter is removed.

In various embodiments, the relative change in volume between themeasured first volume (V1) and the measured second volume (V2), definedas V2−V1/V1, ranges from 5% to 30% of V1. The heating of air in theballoon will result in a volume expansion from 5% at 50° C. to 23% at100° C., so there is a natural expansion of air in the balloon inaddition to expansion of the air in the cavity, causing to an increasein the diameter of the cavity. This increase in diameter cavity willlead to a loosening of the seal created by the balloon(s), resulting inleakage of steam. Therefore, balloon volume must be controlleddynamically to insure a consistent and sufficient seal as cavitydiameter changes.

The delivery of the steam causes the occlusion volume (second volume) tonot be consistently reliable because the body cavity expands in additionto the balloon expanding, hence the need for dynamic adjustment. In someembodiments, a first pressure and a first volume are measured when theballoon walls contact the walls of the cavity. This occurs when a pushback by the cavity walls indicates more pressure is required to increasethe size of the cavity. In addition, the cavity expands with steam.Expansion of the cavity leading to an increase in cavity size due tosteam will depend on the temperature of the steam (for example, 100°C.). As the cavity expands due to steam, the balloon becomesnon-occlusive if it remains at the originally measured second volume.Therefore, in an embodiment, temperature and pressure in the balloon aremeasured and when the temperature and/or pressure decrease below apredetermined value, additional air is pumped to further inflate theballoon. Other variables, such as the type of organ being treated (forexample, more elastic versus less elastic tissue) will also determinethe predetermined temperature and pressure threshold values. Therefore,in an embodiment, a constant second occluding pressure (P2), measuredrelative to a first baseline pressure (P1) is maintained byadding/subtracting air to/from the balloon. In various embodiments, P2measures within a range of 100%-200% of P1.

In various embodiments, the catheters of the present specificationfurther include at least one thermally conducting element attached tothe positioning element. The at least one thermally conducting elementis configured to physically contact, and, in some embodiments,penetrate, a target tissue and enhance the delivery of thermal energyinto the target tissue for ablation. FIG. 40F is an illustration of oneembodiment of a positioning element 4071 of an ablation catheter 4070,depicting a plurality of thermally conducting elements 4072 attachedthereto. In various embodiments, the positioning element 4071 is aninflatable balloon. The positioning element, or balloon 4071, isinflated to a first volume to bring the thermally conducting elements4072 into contact with a target tissue. An ablative agent is thendelivered to the target tissue through the catheter 4070 and out via atleast one delivery port at the distal end of the catheter 4070. Thermalenergy from the ablative agent is transferred from the lumen of thecatheter 4070 into the air in the balloon 4071, further expanding thevolume of the balloon 4071 and pushing the thermally conducting elements4072 further into the target tissue. Thermal energy from the air in theballoon 4071 is transferred to the thermally conducting elements 4072and is released into the target tissue for ablation. In variousembodiments, the thermally conducting elements 4072 comprise solid orhollow metal spikes or needles. In various embodiments, the balloon 4071is composed of a thermally insulating material so that ablative thermalenergy is predominantly transferred from the thermally conductingelements 4072 into the target tissue.

FIG. 40G is an illustration of one embodiment of a positioning element4071 of an ablation catheter 4070, depicting a plurality of hollowthermally conducting elements 4073 attached thereto. In one embodiment,each hollow thermally conducting element 4073 includes a valve 4083 atthe inlet from a lumen of the positioning element 4071 to a lumen of thehollow thermally conducting element 4073. In various embodiments, thepositioning element 4071 is an inflatable balloon. The positioningelement, or balloon 4071, is inflated to a first volume to bring thethermally conducting elements 4072 into contact with a target tissue. Anablative agent is then delivered to the target tissue through thecatheter 4070 and out via at least one delivery port at the distal endof the catheter 4070. Thermal energy from the ablative agent istransferred from the lumen of the catheter 4070 into the air in theballoon 4071, further expanding the volume of the balloon 4071 andpushing the thermally conducting elements 4073 further into the targettissue. Thermal energy from the air in the balloon 4071 is transferredto the thermally conducting elements 4073 and is released into thetarget tissue for ablation. In various embodiments, the thermallyconducting elements 4073 comprise hollow metal spikes or needles. Thethermally conducting elements 4073 include at least one opening at theirdistal ends which are in fluid communication with a lumen of thethermally conducting elements 4073, which, in turn, is in fluidcommunication with the interior of the balloon 4071. As seen in thecross section of the catheter 4070, vapor follows a first pathway 4084to pass from the interior of the balloon 4071, through the thermallyconducting elements 4073, and out to the target tissue. In oneembodiment, each thermally conducting element 4073 includes a valve 4083positioned at its junction with the balloon 4071 to control the flow ofvapor into each hollow thermally conducting element 4073. In oneembodiment, the vapor also follows a second pathway 4085 into theinterior of the balloon 4071 to transmit thermal energy and assist inballoon expansion 4071. In another embodiment, flexible tubes 4086connect the lumen of each thermally conducting element 4073 with a lumenof the catheter 4070, bypassing the interior of the balloon 4071. In oneembodiment, the tubes 4086 are composed of silicone. In this embodiment,the vapor can only travel via the first pathway 4084 and air 4087 isused to expand the balloon 4071. In various embodiments, the balloon4071 is composed of a thermally insulating material so that ablativethermal energy is predominantly transferred from the thermallyconducting elements 4073 into the target tissue. In various embodiments,the thermally conducting elements 4073 possess shape memory propertiessuch that they change shape from being generally parallel to thecatheter 4070 at a temperature below a patient's body temperature tobeing generally perpendicular to the catheter 4070 at temperatures abovethe patient's body temperature.

In other embodiments, the balloons, or positioning elements, are alsothermally conducting and include at least one thermally conductingelement within. FIG. 40H is an illustration of an ablation catheter 4075having a plurality of thermally conducting elements 4077 within apositioning element 4076, in accordance with one embodiment of thepresent specification. The positioning element, or balloon 4076, isinflated to a first volume to bring the balloon 4076 into contact with atarget tissue. An ablative agent is then delivered to the catheter 4075via an inlet port 4074 at its proximal end. The ablative agent isconverted to vapor by the transfer of thermal energy from a heatexchange unit 4078 into the lumen of the catheter 4075. The vaportravels through the catheter 4075 and out via at least one delivery port4079 at its distal end. Thermal energy from the ablative agent istransferred from the lumen of the catheter 4075 into the air in theballoon 4076, further expanding the volume of the balloon 4076 andbringing the thermally conducting elements 4077 into close thermalcontact with the target tissue. Thermal energy from the air in theballoon 4076 and from the lumen of the catheter is transferred to thethermally conducting elements 4077 and is released into the targettissue for ablation. In various embodiments, the thermally conductingelements 4077 comprise solid or hollow metal spikes, needles or strips.In various embodiments, the thermally conducting elements 4077 possessshape memory properties such that they change shape from being generallyparallel to the catheter 4075 at a temperature below a patient's bodytemperature to being generally perpendicular to the catheter 4075 attemperatures above the patient's body temperature.

In other embodiments, a portion of the outer surface of the balloons, orpositioning elements, includes at least one thermally conductingelement. FIG. 40I is an illustration of an ablation catheter 4080 havinga thermally conducting element 4082 attached to an outer surface of apositioning element 4081. The positioning element, or balloon 4081, isinflated to a first volume to bring the thermally conducting element4082 into contact with a target tissue. An ablative agent is thendelivered to the target tissue through the catheter 4080 and out via atleast one delivery port at the distal end of the catheter 4080. Thermalenergy from the ablative agent is transferred from the lumen of thecatheter 4080 into the air in the balloon 4081, further expanding thevolume of the balloon 4081 and pushing the thermally conducting element4082 further against the target tissue. Thermal energy from the air inthe balloon 4081 is transferred to the thermally conducting element 4082and is released into the target tissue for ablation. In variousembodiments, the thermally conducting element 4082 comprises a metalstrip. In various embodiments, the balloon 4081 is composed of athermally insulating material so that ablative thermal energy is onlytransferred from the thermally conducting element 4082 into the targettissue. In various embodiments, the pressure of the balloon isconstantly monitored to prevent over inflation of the balloon. Thepressure of the balloon controls the rate of flow of thermal energy.

In one embodiment, a small, high-speed fan 4012 provides air cooling tothe induction coil 4005 to permit continuous operation without the riskof damage to the coil 4005 or heating chamber 4004. In one embodiment,the fan 4012 is manually controlled by a switch on the front panel of amain enclosure housing the induction coil drive electronics. In variousembodiments, the system 4000 includes a foot switch 4022 for controllingdelivery of steam and to free the hands of the operator during aprocedure. In one embodiment, the foot switch 4022 connects with a ¼″standard audio plug into a corresponding jack (depicted as jack 4113 inFIG. 41B) on a front panel of one of the system electronics enclosures.When pressed, the foot switch 4022 sends a digital signal to a digitalinput terminal of a digital acquisition card. The signal is thenacquired, processed and displayed by a graphical user interface (GUI)4031 of a controller unit 4030. In one embodiment, the foot switch 4022acts in parallel to a large “Deliver Rx” button under a tab with thesame name on the GUI, as described with reference to the system softwarebelow. To start a selected therapy (Rx) program, the operator can eitherpress the “Deliver Rx” button on the GUI or press the foot switch 4022.

The ablation system 4000 includes a plurality of electronics componentsfor operating and monitoring the system. In various embodiments, theelectronics include, but are not limited to, data acquisition andcontrol electronics 4024, induction coil electronics 4026, andthermocouple electronics 4028. A controller unit 4030, comprising agraphical user interface (GUI) 4031, interfaces with the dataacquisition and control electronics 4024 and with the thermocoupleelectronics 4028. In various embodiments, the controller unit 4030comprises a laptop or tablet PC. In one embodiment, the controller unit4030 interfaces with the data acquisition and control electronics 4024and thermocouple electronics 4028 via USB connections. The dataacquisition and control electronics 4024 interface with the inductioncoil electronics 4026, which control energy delivered to the inductioncoil 4005.

In various embodiments, the ablation system 4000 includes one or moresensors configured to sense operational parameters of the system 4000and relay the sensed data to electronics components. In the picturedembodiment, the system 4000 includes a first temperature sensor, orthermocouple 4032, at the steam outlet port of the heating chamber 4004.The first thermocouple 4032 measures the temperature of the steamexiting the heating chamber 4004 and relays this information to thethermocouple electronics 4028. A second thermocouple 4034 is positionedat the core of the heating chamber 4004. The second thermocouple 4034measures the temperature of the heating chamber core and relays thisinformation to the thermocouple electronics 4028. A third thermocouple4036 is positioned at the induction coil 4005. The third thermocouple4036 measures the temperature of the induction coil 4005 and relays thisinformation to the thermocouple electronics 4028. In the picturedembodiment, the system 4000 also includes a pressure sensor 4038positioned at the inlet port of the heating chamber 4004. The pressuresensor 4038 measures pressure at the inlet port of the heating chamber4004 and relays this information to the data acquisition and controlelectronics 4024. In one embodiment, the pressure sensor 4038 is in-linewith the path of the fluid and the system 4000 shuts down heating when apredetermined pressure is sensed.

During operation, the system 4000 is controlled and monitored inreal-time using the data acquisition and control electronics 4024 andcontroller unit 4030. In one embodiment, the data acquisition andcontrol electronics 4024 comprises a National Instruments DAQ card(USB-6009) and an Arduino Mega 2560 microcontroller board. In variousembodiments, the controller unit 4030 controls the following subsystems:temperature controlled core heating; the dosing pump 4006 via operatorcontrol on the GUI, a pre-determined program, or optional foot switch4022; the induction heating chamber 4004 via setting the power level tothe induction coil 4005, manually energizing the induction coil 4005 ata selected power level, or temperature controlling the heater coreautomatically; water pressure monitoring at the inlet port of theheating chamber 4004 to sense any blockage downstream, particularly whenusing a small bore catheter; steam temperature monitoring at the outletport of the heating chamber 4004 (or at the luer lock or proximal end ofthe catheter 4010); heating chamber core temperature monitoring;induction coil 4005 temperature monitoring; monitoring of the currentdrawn by the induction coil 4005 to estimate input power and protect thesystem from over-current situations.

In various embodiments, the vapor ablation system 4000 includes thefollowing specifications: steam generation of 15-150 ml/sec; a maximumsteam temperature of 120° C.; pressure capability up to 25 PSIG; powerconsumption of less than 1000 W; power connection to a standard outlet120V AC/15 A; temperature stabilized and controlled heater core up to200° C.; and phase controlled, self-limiting heater power up toapproximately 500 W at maximum setting. In various embodiments, for aparticular procedure, a maximum volume of steam is delivered over amaximum time of continuous use, with the initial volume of steam beingemitted within a specific time period of activating a button forreleasing the steam. This requires a specific minimum volume of water.

The volume of steam delivered for each procedure is dependent on thesteam temperature and the pressure in accordance with the ideal gasequation as discussed with reference to FIG. 40B. 1 mol of water isequal to 18 g of water. 1 g of water equates to 1 ml of water andtherefore 1/18 mol of water. 1 mol of any gas at the National Instituteof Standards and Technology (NIST) standard conditions (20° C. and101.325 kPa) has a volume of 22.4 L. Therefore, 1/18 mol of vapor atstandard conditions would have a volume of 1,244 ml (22.4 L/18). Invarious embodiments, the vapor has a temperature ranging from 99° C. to101° C. In one embodiment, during operation, the vapor, or wet steam,has a temperature of 100° C. and therefore the volume is increased to1,584 ml (1,244 ml*373K/293K).

In some embodiments, the vapor delivery systems of the presentspecification use we steam, rather than dry steam, to ablate bodytissues, wherein wet steam is defined as steam below its saturationtemperature and which contains water droplets while dry steam is definedas steam at or above its saturation temperature. In various embodiments,the vapor delivery systems of the present specification generate wetvapor having a water vapor content ranging from 1%-99% water vapor and,more preferably, ranging from 5%-95% water vapor. In variousembodiments, application of steam to a body cavity using the vapordelivery systems of the present specification expands the cavity walland results in a 5%-25% pressure increase within the cavity relative toa baseline, pre-treatment pressure. In various embodiments, applicationof steam to a body cavity using the vapor delivery systems of thepresent specification expands the cavity wall and results in a 5%-25%volume increase of the cavity relative to a baseline, pre-treatmentvolume.

Operational parameters are provided below for a variety of vaporablation procedures. In each procedure, the solid metal core of theheating chamber (discussed in detail with reference to FIGS. 46A through46C below) is preheated to a temperature in a range of 200-250° C. Themetal core temperature is then increased to a range of 250-300° C. oncetherapy (vapor delivery) is started. The metal core temperature returnsto the preheated range of 200-250° C. on cessation of each cycle oftherapy.

Barrett's Esophagus Ablation Example 1

Water is delivered at a rate of 5 ml/min into the heating chamber tocontact an outer surface of the solid metal core. Each cycle is on for 5seconds and off for 10 seconds for a total of 5 cycles, which willconvert the water into approximately 132 ml steam/sec during the onphase of each cycle. At a water flow rate of 5 ml/min, steam at 100° C.will be generated at a rate of 7,920 ml/min (132 ml/sec).

Example 2

Water is delivered at a rate of 5 ml/min into the heating chamber tocontact an outer surface of the solid metal core. Each cycle is on for10 seconds and off for 10 seconds for a total of 5 cycles, which willconvert the water into approximately 132 ml steam/sec during the onphase of each cycle.

Endometrial Ablation Example 1

Water is delivered at a rate of 10 ml/min into the heating chamber tocontact an outer surface of the solid metal core. Each cycle is on for30 seconds and off for 30 seconds for a total of 5 cycles, which willconvert the water into approximately 264 ml steam/sec during the onphase of each cycle.

Example 2

Water is delivered at a rate of 10 ml/min into the heating chamber tocontact an outer surface of the solid metal core. Each cycle is on for60 seconds and off for 60 seconds for a total of 3 cycles, which willconvert the water into approximately 264 ml steam/sec during the onphase of each cycle.

Example 3

Water is delivered at a rate of 5 ml/min into the heating chamber tocontact an outer surface of the solid metal core. Each cycle is on for90 seconds and off for 90 seconds for a total of 2 cycles, which willconvert the water into approximately 132 ml steam/sec during the onphase of each cycle.

Example 4

Water is delivered at a rate of 10 ml/min into the heating chamber tocontact an outer surface of the solid metal core, generating vapor at arate of −264 ml/sec. The vapor is delivered until an intracavitypressure reaches 50 mm Hg. During each cycle, the pressure is maintainedat 50 mm Hg (+/−20%) with continuous vapor delivery (on period) for 60sec and then thermal delivery is turned off (off period) for 60 sec. Atotal of 2 cycles of vapor delivery are performed. The flow of vapor isvaried from 0-264 ml/sec to maintain a desired intracavity pressure forthe duration of the therapy. At 50 mm Hg pressure, the volume of thedelivered steam decreases to 247.7 ml/sec (264 ml/sec*760 mm/810 mm)from its volume at standard conditions.

Example 5

Water is delivered at a rate of 5 ml/min into the heating chamber tocontact an outer surface of the solid metal core, generating vapor at arate of −132 ml/sec. The vapor is delivered until an intracavitypressure reaches 50 mm Hg. During a first cycle, the pressure ismaintained at 50 mm Hg (+/−20%) with continuous vapor delivery (onperiod) for 60 sec and then thermal delivery is turned off (off period)for 60 sec. A second cycle, having an on period of 90 sec and an offperiod of 90 sec, is performed and then the therapy is concluded. Theflow of vapor is varied from 0-132 ml/sec to maintain a desiredintracavity pressure for the duration of the therapy.

Example 6

Water is delivered at a rate of 5 ml/min into the heating chamber tocontact an outer surface of the solid metal core, generating steam at arate of −132 ml/sec. The steam is delivered for 90 seconds. Theintracavity pressures are maintained at −50 mm Hg throughout thedelivery of steam.

Prostate Ablation Example 1

Water is delivered at a rate of 1 ml/min into the heating chamber tocontact an outer surface of the solid metal core. Each cycle is on for10 seconds and off for 60 seconds for a total of 10 cycles, which willconvert the water into approximately 26.4 ml steam/sec during the onphase of each cycle.

Example 2

Water is delivered at a rate of 2 ml/min into the heating chamber tocontact an outer surface of the solid metal core. Each cycle is on for 5seconds and off for 60 seconds for a total of 5 cycles, which willconvert the water into approximately 52.8 ml steam/sec during the onphase of each cycle.

Example 3

Water is delivered at a rate of 5 ml/min into the heating chamber tocontact an outer surface of the solid metal core. Each cycle is on for 2seconds and off for 30 seconds for a total of 10 cycles, which willconvert the water into approximately 132 ml steam/sec during the onphase of each cycle.

Vessel Ablation Example 1

Water is delivered at a rate of 5 ml/min into the heating chamber tocontact an outer surface of the solid metal core. Each cycle is on for10 seconds and off for 30 seconds for a total of 3 cycles, which willconvert the water into approximately 132 ml steam/sec during the onphase of each cycle.

Example 2

Water is delivered at a rate of 5 ml/min into the heating chamber tocontact an outer surface of the solid metal core. Each cycle is on for20 seconds and off for 40 seconds for a total of 2 cycles, which willconvert the water into approximately 132 ml steam/sec during the onphase of each cycle.

Bleeding Gastric Ulcer Example 1 Bleeding Ulcer

Water is delivered at a rate of 10 ml/min into the heating chamber tocontact an outer surface of the solid metal core. Each cycle is on for10 seconds and off for 10 seconds for a total of 5 cycles, which willconvert the water into approximately 264 ml steam/sec during the onphase of each cycle.

Example 2 Bleeding Angioectasia

Water is delivered at a rate of 5 ml/min into the heating chamber tocontact an outer surface of the solid metal core. Each cycle is on for 5seconds and off for 10 seconds for a total of 3 cycles, which willconvert the water into approximately 132 ml steam/sec during the onphase of each cycle.

Bronchial Ablation Example 1

Water is delivered at a rate of 2 ml/min into the heating chamber tocontact an outer surface of the solid metal core. Each cycle is on for 5seconds and off for 10 seconds for a total of 5 cycles, which willconvert the water into approximately 52.8 ml steam/sec during the onphase of each cycle.

Example 2

Water is delivered at a rate of 1 ml/min into the heating chamber tocontact an outer surface of the solid metal core. Each cycle is on for10 seconds and off for 10 seconds for a total of 5 cycles, which willconvert the water into approximately 26.4 ml steam/sec during the onphase of each cycle.

Sinus Ablation Example 1

Water is delivered at a rate of 1 ml/min into the heating chamber tocontact an outer surface of the solid metal core. Each cycle is on for30 seconds and off for 30 seconds for a total of 5 cycles, which willconvert the water into approximately 26.4 ml steam/sec during the onphase of each cycle.

Polyp Ablation Example 1

Water is delivered at a rate of 5 ml/min into the heating chamber tocontact an outer surface of the solid metal core, generatingapproximately 132 ml steam/sec. The polyp is grasped and the steamdelivered until the visible tissue turns white. Pressure is applied totransect the tissue while simultaneously applying vapor until the tissueis completely transected. If bleeding is visualized, the pressure isreleased and the vapor is continuously applied until bleeding ceases.Once bleeding has been stopped, pressure transection and vapor ablationis continued.

FIG. 40J is a flowchart listing the steps of a method of using a vaporablation system in accordance with one embodiment of the presentspecification. At step 4064, the heating chamber is heated to apre-treatment temperature T₁. Room temperature water is delivered to theheating chamber at step 4065. Then, at step 4066, the temperature of theheating chamber is increased to a treatment temperature T₂ just prior tothe arrival of the water into the heating chamber. In variousembodiments, T₂ is at least 10% greater than T₁. The temperature of theheating chamber at T₂ vaporizes the water in the heating chamber. Thevapor created in the heating chamber is delivered to the target tissueat step 4067. At step 4068, delivery of water to the heating chamber isstopped to conclude treatment. The temperature of the heating chamber isthen decreased to a post-treatment temperature T₃ at step 4069. Invarious embodiments, T₃ is at least 10% less than T₂. The steps may berepeated to deliver multiple treatment cycles.

FIG. 40K is a flowchart listing the steps of a method of using a vaporablation system in accordance with another embodiment of the presentspecification. At step 4093, a first voltage V₁ is applied to theinduction coil to heat the heating chamber to a pre-treatmenttemperature T₁. Room temperature water is delivered to the heatingchamber at step 4094. Then, at step 4095, the first voltage V₁ isincreased to a second voltage V2 to increase the temperature of theheating chamber to a treatment temperature T₂ just prior to the arrivalof the water into the heating chamber. In various embodiments, V2 is atleast 10% greater than V₁ and T₂ is at least 10% greater than T₁. Thetemperature of the heating chamber at T₂ vaporizes the water in theheating chamber. The vapor created in the heating chamber is deliveredto the target tissue at step 4096 while the higher temperature in theheating chamber is maintained. At step 4097, delivery of water to theheating chamber is stopped to conclude treatment. The second voltage V2is then reduced to a third voltage V3 at step 4098 to decrease thetemperature of the heating chamber to a post-treatment temperature T₃.In various embodiments, V3 is at least 10% less than V2 and T₃ is atleast 10% less than T₂. The steps may be repeated to deliver multipletreatment cycles.

System Hardware

FIG. 41A is an illustration of the components of a vapor ablation system4100 in accordance with one embodiment of the present specification. Thevapor ablation system 4100 includes a controller unit 4130, or tabletPC, a USB hub 4140, and a power block 4142. In one embodiment, the USBhub 4140 is a 7-port USB hub and the power block 4142 is a 4-outlet ACconnector block so that only a single AC power plug is needed to operatethe system. The power block 4142 includes two AC adapters, a firstadapter to charge the controller unit 4130 and a second adapter tosupply external power to the USB hub 4140. The controller unit 4130, ortablet PC, does not need to supply any power to the USB devices as poweris supplied directly to the USB hub 4140 by the power block 4142. Thisbecomes particularly beneficial when the controller unit 4130 isoperating in battery mode, conserving battery power of the controllerunit 4130 and therefore prolonging battery life. The two remainingoutlets on the power block 4142 provide convenience for connecting andpowering any additional devices in the future. The USB hub 4140 expandsthe controller unit's 4130 limited USB connectivity and permits furtherflexibility and expansion in the future.

The system 4100 also includes a water reservoir 4102, a cover 4144 overthe heating chamber and induction coil, and system electronics 4150,4152, 4154. The outlet port 4146 of a manifold attached to the distalend of the heating chamber is visible protruding through cover 4144. Thecontroller unit 4130 interfaces with the system electronics 4150, 4152,4154 via USB connections through the USB hub 4140. An induction coildriver circuit is located within system electronics 4150, whichcomprises a heavy-gauge steel shielded enclosure. Data acquisitionelectronics and a circuit board with cable interconnects and signalprocessing electronics are located within system electronics 4152. Theinduction coil driver circuit and data acquisition electronics comprisethe control electronics for the induction coil. The induction coildriver circuit is located within a shielded enclosure because itoperates in switch-mode which is known for creating electronic noisethat can interfere with sensitive sensor signals. The enclosure forsystem electronics 4150 is also shielded because it contains AC linevoltage as well as high-voltage kickback voltage spikes, both of whichare dangerous to operators. In one embodiment, a lid to systemelectronics 4150 includes a lock and key 4151 to prevent unauthorized oraccidental access to the voltages. In one embodiment, the components ofthe vapor ablation system, with the exception of the controller unit4130, are secured to a backboard 4101.

FIG. 41B is an illustration of the vapor ablation system 4100 of FIG.41A with the heating chamber cover removed. The controller unit and USBhub are also removed in FIG. 41B. With the cover removed, the heatingchamber 4104 and induction coil 4105 are visible. Also visible are thefront end electronics of the thermocouple electronics 4128. The frontpanel of system electronics 4150 includes an on/off fan switch 4127 anda power indication light 4129. FIG. 41B also depicts the front end of adata acquisition card 4124 contained within system electronics 4152. Thecard 4124 includes an LES operation status light 4125 and a USB port4126. The card 4124 receives a voltage of 0-5 V that is determined usinga numeric control on the GUI. The analog output of the card 4124 isconverted to a pulse train of variable frequency in avoltage-to-frequency converter. The pulse train is further conditionedto maintain a 50% duty cycle, independent of frequency, as required by astepper motor controller of the pump. The 50% duty cycle, variablefrequency pulse train is input to a stepper motor driver circuit. Thestepper motor driver circuit translates the pulse train into theappropriate wave forms that energize two coils of the stepper motor,resulting in the controlled movement of the motor's armature in speedand direction. The known and controlled shaft speed of the motordirectly drives the pump head of the positive displacement pumpresulting in known and controlled water flow. After careful calibration,this signal chain thus allows the operator to set a flow rate in unitsof ml/min on the GUI and the resulting water flow to the heater chamberwill be accurate to approximately ±5%.

FIG. 41C is a close-up illustration of the uncovered heating chamber4104 and induction coil 4105 of the vapor ablation system of FIG. 41B.The heating chamber 4104 includes a manifold 4148 covered by a thermallyinsulating material attached to its distal end. A luer lock connector4149 is positioned at an outlet port of the manifold 4148. Also depictedin FIG. 41C is a terminal block 4147 to which a plurality ofthermocouple leads are connected. The thermocouples are used to sensetemperatures within the system as described with reference to FIGS. 49Athrough 49G. In one embodiment, the water reservoir 4102 includes awater level sensor 4103. When the water level is low within thereservoir 4102, the sensor 4103 sends a digital signal to a digitalinput terminal of a data acquisition card. The signal is then acquiredand displayed by the GUI. In one embodiment, the sensor activates whenthe water level drops approximately to ⅓ of the capacity of thereservoir. An alarm is displayed and a sound is generated by the GUI towarn the user to refill the water reservoir 4102.

FIG. 41D is an illustration of the vapor ablation system 4100 of FIG.41A with the covers removed from the system components. The system 4100includes a 4-outlet power block 4142 which provides additional ACoutlets for auxiliary devices such as a computer charge adapter and a 5VDC adapter to externally power the USB hub 4140. The use of a USB hub4140 provides the convenience of requiring only one USB cable to thecontroller unit, or tablet computer, to control the entire system. Thesystem 4100 also includes a microcontroller board inside a shielding box4162 and a water reservoir 4102. Also depicted in FIG. 41D are a dosingpump 4164 and the heating chamber 4104. A heavy-gauge steel enclosure4165 with hinged lid the accommodates the power electronics to drive theinduction coil as well as circuit boards for power phase control, statusindication, current-sensing circuitry, 12V power supply for a coolingfan and pump and an AC current meter. An RMS clamp-on ammeter 4169 withreadout and signal conditioning circuit is located within theheavy-gauge steel enclosure 4165. The clamp-on ammeter 4169 monitors thecurrent drawn by the induction power circuit of the system which is adirect measure of the energy supplied to the heater core and thus to thewater to generate steam.

FIG. 41E is a close-up illustration of the dosing pump 4164 andheavy-gauge steel enclosure 4165 of the vapor ablation system of FIG.41A. Referring to FIG. 41E, the lid 4163 of the heavy-gauge steelenclosure 4165 is in place. The lid includes two status lights labeled“SYSTEM OK” 4166 and “ARMED STATUS” 4167. The “SYSTEM OK” 4166 statuslight illuminates green and indicates that the oscillator of the powerswitching circuit is free-running. This light must be lit green any timethe mains power switch is turned on. If the light is not illuminated,then there is a system fault that must be investigated. The “ARMEDSTATUS” 4167 status light illuminates red and indicates that theinduction power drive is enabled, feeding the coil with resonantcurrent. This light will illuminate when the heater is activatedmanually or engaged programmatically.

FIG. 41F is a close-up illustration of the dosing pump 4164, with intakeport 4155 and discharge ports 4156, of the vapor ablation system of FIG.41A. The pump 4164 provides a highly controlled flow of water into theheating chamber nearly independent of back pressure. In one embodiment,the pump 4164 is a valve-less, reciprocating-and-rotating piston pumpwith a tilt-mounted pump head 4157 to adjust the stroke volume perrevolution. In one embodiment, the piston and cylinder of the pump 4164are precision-ground and do not require any lubrication. In oneembodiment, the pump 4164 is self-priming, capable of generating veryhigh pressures and its flow rate can be directly related to therevolutions of the drive shaft. The pump 4164 is driven by a steppermotor 4158 which precisely translates a signal pulse rate into shaftspeed and thus flow rate. Drive electronics for the stepper motor 4158are located inside a pump pedestal 4159. Water from a reservoir isdelivered via the intake port 4155 into the pump head 4157. The pump4164 then pumps the water via two discharge ports 4156 into an enclosure4133. A pressure sensor 4135 is mounted to the enclosure 4133 forsensing the pressure of the water being delivered by the pump 4164. Thepressure sensor 4135 is able to detect blockages downstream from thepump 4164. The sensor is excited with 5V DC and outputs 0.5-4.5V as thepressure varies from 0-25 PSIG. The voltage is read by an analog inputterminal of the data acquisition card and acquired and displayed by theGUI. An output port 4136 delivers water from the enclosure 4133 to theheating chamber. By controlling the pulse rate to the stepper motordriver circuit, the shaft speed and therefore the flow rate of the pump4164 can be precisely calibrated. This is the basis of the flow ratesetting in the graphical user interface (GUI) and the determination ofthe actual flow rate of water into the heater chamber. Since the pump4164 is a reciprocating positive displacement type pump, it deliverswater in well-defined strokes which results in pulsating pressure andflow characteristics. To minimize pulsations, in one embodiment, thepump head 4157 tilt angle is adjusted to the minimum angle required todeliver at least 5.0 ml/min flow at the highest reliable stepper motorspeed.

FIG. 41G is a close-up illustration of the main electronics board 4170with ancillary electronics within the heavy-gauge steel enclosure of thevapor ablation system of FIG. 41A. The main electronics board 4170includes the large power components of the induction coil drive stage,such as IGBT switching devices mounted below a large heat sink, filterand resonant capacitors, toroidal filter inductors and the smallerpassive and active components of the IGBT gate driver electronics andcontrol logic. A status indicator board 4171 controls the statusindicator lights described with reference to FIG. 41E. A triac phasecontrol circuit 4172 controls the power delivered by the induction drivecircuit. Block capacitors 4178 are positioned above and below the triacphase control circuit 4172. The triac phase control circuit 4178 ispositioned proximate the main power entry terminals to minimize thelength of the cables that carry large currents and separate them fromthe more sensitive electronics to minimize noise pickup. Thecurrent-sensing circuitry employs a commercial clamp-on AC current meterand ties into its processing electronics. Circuit board 4173 comprisessignal-processing circuitry to form a DC signal from the sensed ACcurrent to be read by the data acquisition system. The main electronicsboard 4170 further includes a miniature, high-speed fan 4174 used tocontinuously air-cool the induction coil. In one embodiment, the fan4174 may be switched off on a front panel of the heavy-gauge steelenclosure with a dedicated switch. The fan 4174 also provides cooling ofthe IGBT heat sink 4175 by moving air in the vicinity of the intake. A12V/2 A switching power supply 4176 supplies power to the pump, fan4174, and signal processing electronics located on the outside of theenclosure lid. A resistor 4177 ensures proper operation of an inductioncircuit described with reference to FIGS. 41H and 411 below. In oneembodiment, the resistor 4177 has a value of 1.5 kΩ.

FIG. 41H is a block diagram of the induction heater drive electronics4180 in accordance with one embodiment of the present specification. Thecircuit used in the electronics is based on single-ended inductionheating topology. It uses a high-current, high-voltage semiconductorswitching device, in the form of an insulated-gate bipolar transistor(IGBT) 4181, to momentarily apply rectified line voltage across a tankcircuit (L_(r) and C_(r)) 4182, of which the inductor coil L_(r) is theinductivity. In some embodiments, the insulated-gate bipolar transistoris configured to be switched at a frequency in a range of 20 kHz to 100kHz. Referring to FIG. 41H, the tank circuit 4182 is a parallel tankcircuit. In other embodiments, the tank circuit is a series tankcircuit. In some embodiments, the semiconductor switching device is ametal-oxide-semiconductor field-effect transistor (MOSFET). Thecontrolled switch is timed to approximately match the resonancefrequency of the tank circuit 4182. A rectifier 4185 receivesalternating current line voltage and provides direct current power. Thepower delivered to the induction coil is controlled by a phase-controlcircuit 4184 using a triac phase control circuit, essentially connectingthe AC line voltage to the rectifier 4185 at a precisely timed moment ofeach half-wave of the AC line voltage. In some embodiments, thephase-control circuit 4184 is configured to connect the AC line voltageto the rectifier 4185 at only a portion of each half-wave of the AC linevoltage, thereby controlling the amount of energy transferred to thesemiconductor switching device. At each half-wave of the line voltage,the resonant circuit is actively driven, for example, by an H bridgeinverter as described below, to replenish lost energy, and is notallowed to resonate on its accord. In some embodiments, thephase-control circuit 4184 is configured to adjust the energytransferred to the semiconductor switching device according to afeedback loop. The triac phase-control circuit 4184 commutates (switchesitself off) at the zero-crossing points of the line voltage. Therefore,it must be re-triggered for every AC half-wave and means that the powercontrol has a resolution of 83 ms (1 second/120 half-waves for a 60 Hzline frequency) and can therefore be very responsive. The triacphase-control circuit 4184 allows the switch to pass or transfer afraction of the power contained in the AC line to the induction powercircuit. The IGBT gate drive 4181 circuit (or MOSFET) operatescontinuously. An H bridge inverter circuit is included and configured toapply rectified line voltage across the resonant circuit at certaintimes and with a certain polarity as to periodically drive the resonantcircuit such that optimal energy transfer is facilitated to the resonantcircuit. The H bridge inverter circuit is adapted to switch off when amagnetic field generated by the induction coil is fully saturated. Insome embodiments, a frequency of the H bridge inverter circuit isbetween 10 kHz and 100 kHz. In some embodiments, the H-bridge invertercomprises four switches and every 10 μsec to 50 μsec two of the fourswitches are switched closed and two of the four switches are switchedopen such that every 10 μsec to 50 μsec the magnetic field is driven tozero and a polarity of the magnetic field is reversed.

In one embodiment, the magnetic field generated about the metal core ofthe heating chamber has a vibration of 15-25 kHz. The conversion ofelectrical energy into heat energy is very efficient. The induction coilis driven in the power stage with high amps and high current linevoltage. An oscillating circuit turns the switches of the inductionheater drive electronics 4180 on and off approximately 15,000 times persecond. The voltage is rectified and filtered 4185 to produce a DVvoltage of approximately 170 V. Once the magnetic field generated by theinduction coil is fully saturated, the switches are turned off bycontrol circuitry to prevent blowing the fuse to the system. Once theswitches are turned off, all of the energy is contained in the magneticfield. The magnetic field collapses and the coil discharges the energyinto an electric pulse. The electrical energy is input at 120 V AC,rectified and filtered to 170 V DC, and up to a 1000 V electricalkickback pulse is generated, in the opposite direction, when theswitches are turned off and the magnetic field collapses. In oneembodiment, as seen in FIG. 41G, the system includes two capacitors 4178which absorb the energy from the kickback pulse. The capacitors thendischarge the energy back into the coil. During this process, the metalcore of the heating chamber absorbs a large amount of the energy (toconvert to heat energy) so only some energy oscillates between the coiland the capacitors. The frequency of the line voltage is timed acrossthe coil. In one embodiment, when approximately 10% of the electricalenergy remains in the capacitors (i.e. the capacitors have discharged90% of the electrical energy into the coil), the line voltage isswitched back on and the process begins again. In one embodiment, theself-resonance frequency of the capacitors triggers the switches.

FIG. 41I is a graph illustrating waveforms generated by the inductionheater drive electronics (induction circuit) depicted in FIG. 41H. Invarious embodiments, an inductor current 4186 is semi-sinusoidal,meaning it approaches the ideal waveform. In one embodiment, theinductor circuit generates a sinusoidal wave form. The voltage acrossthe IGBT device 4187 is instructive to follow the waveform through onecycle. When the IGBT is conducting (switch is closed), energy istransferred into the inductor to build up its magnetic field and thecapacitor is also partially charged. Upon opening of the switch, theparallel resonant tank circuit undergoes self-oscillation at its naturalresonance frequency. At the time t₁ 4121, the IGBT's gate is driven andthe device is turned on, resulting in a collapse of the voltage acrossthe device as indicated by V_(CE)≈0. This is the equivalent of closingthe switch. The inductor current 4186 rises relatively slowly as itbuilds up the magnetic field in the inductor, a process that does notoccur instantaneously because of the self-induction of the inductivitywhich opposes any current change with a voltage change. At t₂ ₄₁₂₂, theIGBT is turned off and the tank circuit self-resonates. Starting withthe collapsing magnetic field that induces a large induction voltage“kick”, the current begins to flow from the coil into the parallelcapacitor. When the capacitor is fully charged, the capacitor dischargesinto the coil with reverse polarity building up its magnetic field anew,but in the opposite direction. When the capacitor is fully discharged,the energy is transferred back into the coil. At t₆ 4123, the IGBT'sgate is driven again and the cycle repeats. Optionally, in oneembodiment, a resistor, depicted as resistor 4177 in FIG. 41G, assuresthat the oscillator of the gate driver circuitry is free-running forproper operation of the IGBTs. Since the heater core absorbs much of thecoil energy, the wave form is distorted and dampened. In otherembodiments, a half-bridge topology, requiring a pair of switches, or afull-bridge or H-bridge switching topology, requiring 4 switches, isused to increase system efficiency.

FIG. 41J is an illustration of a triac phase control circuit of theinduction heater drive electronics depicted in FIG. 41H. The triacV_(TRIAC) 4188 connects the induction heater power electronics to theline voltage when triggered and disconnects it during the nextzero-crossing of the same AC half wave. The triac's gate is preciselytriggered by an optically-isolated drive circuit controlled by a voltagefrom 0-5V supplied by the analog output of the data acquisition card4124 of FIG. 41B, which in turn is controlled by the GUI.

To create the most efficient generation of steam from an AC primaryinput, the rectified and filtered DC voltage is converted to anappropriate waveform to drive the induction coil. A waveform that issubstantially sinusoidal is preferred. Any distortion in the waveformgenerates harmonics which reduce overall efficiencies and may produceother undesirable side effects, such as acoustic noise and electronicnoise. Such noise may need to be filtered or shielded to not interferewith sensitive control electronics in close proximity within the housingof the steam generator. Creating a sinusoidal waveform from a DC sourceis typically done with linear elements such as transistors. However,operating semiconductors in the linear range generates substantial ohmicheating and is impractical for most high-power applications. High-powerapplications typically use semiconductor power switches such as MOSFETsand triacs. The ohmic losses in the on or off state are small, providedthe transition between these states can be achieved sufficiently fast.

To be able to use switches to produce a sinusoidal waveform, a so-calledresonant inverter circuit is used. In this circuit, the inductionproperty of the coil and the capacitive property of a capacitor are usedto create a series or parallel tank circuit with resonance frequencyapproximately in the desired frequency range. The switches arecontrolled in such a fashion as to drive the resonant circuit toperiodically deliver power while a switch is on and allow the resonantcircuit to oscillate naturally while the switch is off.

The switches must be switched off as fast as possible to minimize thedwell time in the linear region and minimize ohmic losses. During theswitch on-time, the magnetic field in the coil is built up. When theswitch is turned off, the magnetic field collapses creating a largeelectrical induction spike. This spike must be snubbed so not to damagethe switch by exceeding its blocking voltage limit. Snubber capacitorsare typically high-quality, low-loss capacitors that can handle largecurrent surges. This makes these capacitors large and expensive. Also,the induction spike distorts the sinusoidal waveform, creating unwantedharmonics and thus inefficiencies. An H-bridge inverter architecturewith four switches, where the coil is always tied to two closedswitches, can be used to address these inefficiencies. After onehalf-wave, the conducting switches both open and the other previouslyopened switches close, repeating the cycle at the next half-wave.Essentially, this is the equivalent of connecting the coil to a DCsource for a brief period until the magnetic field nearly reachessaturation, at which time the leads are quickly reversed and the DCsource first forces the magnetic field to zero and then increases it inthe reverse polarity until saturation, repeating the cycle all overagain. This is different from a single-ended resonant circuit where theresonant tank circuit is allowed to resonate back on its own accord. Theadvantage of the H-bridge architecture is that the waveform across thecoil is much more sinusoidal, resulting in higher efficiency with lessharmonics and less acoustic or electronic noise.

The high-side switches open and close with a gate-to-source voltage of10V or 0V. However, since the source terminal is tied to the DC bus lineand the potential of this line should be allowed to change to controlthe power delivered to the coil, the gate voltage must change in kind.Use of p-channel MOSFET switches for the high-side switches andn-channel switches for the low-side switches creates a push-pull ortotem-pole drive circuit (with low output impedance) to address thisissue. N-channel MOSFETs are used for the low side switches to avoidhigher ohmic losses during on-time encountered with p-channel MOSFETs,which have inherently significantly higher on-state resistances. Thegate drive circuit must reference its gate voltage to the sourceterminal potential that is tied to the DC bus line. If this DC bus linepotential changes, so must the gate voltage to assure that the off-stateis Vgs=0V and the on-state is Vgs=10V. Since in a high-power applicationthe DC bus potential can easily be around 170 VDC (rectified AC), andideally is variable, there are substantial demands on the gate drivercircuit. Special gate drivers, which use bootstrap capacitors that storeenough energy to drive the gate during the on-state and recharge duringthe off-state while floating up and down with a changing DC bus voltage,are used to address these demands. In some embodiments, a pair oflow-and-high side driver circuits are used to driving an H-bridge. Thedriver circuits must be driven with a properly-timed square waveform. Atotal of 4 square waves are required to drive the 4 MOSFET switches ofthe H-bridge. To avoid a short, the timing of the 4 square waveformsmust be such that the switches are never driven in a shot-throughcondition, wherein the conducting switches have not switched off yetwhile the non-conducting switches are already turned on. Conversely, iftoo much time elapses before turning the other pair of switches on, thenthe resonant circuit is allowed to act on its own, resulting in awaveform across the coil that is distorted, resulting in unwantedharmonics. Therefore, it is important to avoid the shot-throughcondition under all circumstances and to optimize the switchover timessuch that the flow of energy is always in the most efficient form fromthe inverter circuit into the coil. In various embodiments, amicrocontroller is used to generate the 4 required waveforms. Themicrocontroller is configured to adjust the timing and phase relationsof the square waveforms for the gate drivers to produce the optimalsinusoidal waveform across the induction coil.

In order to optimize efficiency during conversion of the magnetic fieldenergy into eddy current and hysteresis losses, it is important toselect the best operating frequency. The eddy current and hysteresislosses are frequency dependent and, in some embodiments, an optimalfrequency ranges between 50 kHz and 100 kHz. At these frequencies, theperiods are approximately 10 μs. Use of bit-banging of a digital pin ona microcontroller peripheral produces a time resolution of 1 μs or lessto adjust the square waveform generated by the microcontroller.

Induction Heating

The induction heating chamber in the vapor ablation systems of FIGS. 40through 41C includes a length and comprises an electrically conductingmaterial within an electrically non-conducting material. In someembodiments, the electrically conducting material is a ferromagneticmaterial. An electrically conducting material can be heated by eddycurrent losses. A ferromagnetic material can be heated by eddy currentlosses as well as magnetic hysteresis losses. In some embodiments, theelectrically non-conducting material is a non-ferromagnetic material. Inone embodiment, the non-ferromagnetic material comprises a cylinder ortube. The non-ferromagnetic tube has a lumen within for receiving theferromagnetic material. In various embodiments, the non-ferromagnetictube is electrically insulating. In some embodiments, the ferromagneticmaterial is a metal and has a shape of a rod. An induction coil iswrapped about the tube. A fluid is passed through a space between therod and tube, extending the length of the heating chamber, where thermalenergy from the induction heating vaporizes the fluid. In variousembodiments, the fluid is water, ionized water, non-ionized water,sterile water, or a solution of a metal salt and water. The coil isenergized with an alternating current (AC) in the same way as a regularelectromagnet. However, since the arrangement is optimized for heatgeneration, the frequency used is between 10-100 s of kHz, much higherthan the 60 Hz line frequency. In essence, the induction coil acts asthe primary of a transformer while the metal rod acts as the secondary.In various embodiments, the magnetic coupling of the heating chamber andcoil arrangement is more than 90% efficient and the conversion ofinduced eddy current into Joule heat inside the metal rod is practically100% efficient. Conversion efficiencies of the magnetic energy into heatenergy within the heating chamber of 30% or higher, including 40, 50,60, 70, 80, 90, and 100%, are within the scope of the invention. Invarious embodiments, a magnetic to heat energy conversion of 60% orhigher is preferred to allow for a form factor for the inductioncoil/chamber that is hand held. In various embodiments, theferromagnetic material comprises any one of, or alloys of, iron, nickel,stainless steel, manganese, silicon, carbon, copper, an electricallyconducting material, an electrically insulating material, or a Curiematerial having a Curie temperature between 60 and 500° C. Since the rodis composed of metal, there are two distinct mechanisms of heatgeneration in the core: a first from eddy currents and a second frommagnetic hysteresis.

FIG. 42 is an illustration of eddy currents induced by an alternatingelectromagnetic field. An applied high-frequency alternating current4204 in an induction coil 4202 induces a rapidly-changing axial magneticfield 4214 of the same frequency in a metal core 4212. This axialmagnetic field 4214 in turn induces rapidly-changing, circular currents,or eddy currents 4224, inside the conducting metal core 4212. Theinduced eddy currents 4224 readily generate Joule heat in the conductorwith practically 100% efficiency.

There is a depth distribution of these induced eddy currents 4224 thatdepends on the frequency and strength of the applied alternating current4204 and the material properties of the core material 4212. This depthdistribution is readily controllable if all parameters are known and canbe used advantageously to primarily heat the exterior of the core wherethe heat is transferred to the water for rapid evaporation. In oneembodiment, the metal core is designed to be hollow so that no energy isused to heat a parasitic center, rather all energy is concentrated onthe surface to be used for steam generation.

FIG. 43 is a graph illustrating the variation in magnetic hysteresisbetween different ferromagnetic and non-ferromagnetic materials. Thethree curves 4301, 4302, 4303 shown are hysteresis traces of anexternally applied magnetic field B_(o) 4305 and the resultingmagnetization M 4310 of the ferromagnetic core material. The upperdash-dotted line 4307 and lower dash-dotted line 4309 indicate thepositive and negative magnetic saturation of the material, respectively.Saturation means that an increasing external magnetic field will notresult in a further increase in magnetization. The phenomenon ofsaturation occurs when all available magnetic domains have alignedthemselves with the external magnetic field, at which point the maximummagnetization has been reached.

As the externally applied magnetic field B_(o) 4305 is reduced towardzero, the magnetic domains tend to remain in their recently alignedorientation, and will only be partially “randomized” by thermal energykT (always positive above the absolute temperature of 0K=−273° C.) ifthe aligning external field B_(o) 4305 is reduced or eliminated. Theretained magnetization M 4310 after removal of the B_(o)-field 4305 iscalled saturation remanence and is higher for magnetically softmaterials as seen in curve 4301, lower for magnetically hard materialsas seen in curve 4302, and zero for non-magnetic materials as seen incurve 4303.

As the externally applied magnetic field is reversed and increased inthe reverse direction, the B_(o)-field 4305 exerts work on the magneticdomains and starts to re-align them in the opposite direction, resultingfirst in a decreased magnetization M 4310 and then in a reversal of themagnetization. Each flipping of a magnetic domain is lossy and causesfriction, generating heat in the core material. As the B_(o)-field 4305is further increased, saturation in the opposite direction is eventuallyreached. Repeating this process traces the hysteresis curves 4311, 4312,4313. More Joule heat is generated as the domains are flipped morequickly.

The hysteresis curves 4311, 4312, 4313 each circumscribe a respectivearea 4321, 4322, 4323. The circumscribed area 4321 is larger inmagnetically soft materials compared to the area 4322 in magneticallyhard materials and to the area 4323 in non-magnetic materials. The area4321, 4322, 4323 is an indication of how many magnetic domains alignedand re-aligned themselves with the externally applied magnetic field andis therefore a measure of how much heat was generated during theprocess. A larger circumscribed means more heat generated inside theferromagnetic core material. Therefore, a soft ferromagnetic materialwill generate greater heat through magnetic hysteresis than a hardferromagnetic material or non-magnetic material.

FIG. 44 is an illustration depicting a variety metal rods 4401, 4402,4403, 4404, 4405 and a covering tube 4410 for an induction heatingchamber in accordance with some embodiments of the presentspecification. Metal rods 4401, 4402, 4403, 4404 each include a threadedouter surface intended to force the water and steam along a spiral pathto increase the time of contact between the rod and the water and steam.Increased contact time can result in better energy transfer to the waterand steam. In various embodiments, the threaded outer surface cancomprise grooves of circular, triangular, trapezoidal, or rectangularcross section. Metal rod 4405 includes a smooth outer surface. The innerdiameter of tube 4410 is only slightly larger than the outer diameter ofthe metal rods 4401, 4402, 4403, 4404, 4405. When the tube 4410 ispositioned coaxially over one of the metal rods, a small space iscreated between the tube 4410 and the metal rod. Water travels throughthis space, contacts the heated metal core, and is converted to steam.In a preferred embodiment, a heating chamber comprises metal rod 4405and tube 4410.

FIG. 45 is an illustration of a metal rod 4502 having a threaded outersurface and a tube 4504 having a threaded inner surface for a heatingchamber in accordance with one embodiment of the present specification.In one embodiment, the outer surface of the rod 4502 and inner surfaceof the tube 4504 include threads matching 5/16″-18 national coarsethread (NC). The tube 4504 fits over the rod 4502 and creates a spiralpath for water and steam to travel.

FIG. 46A is an illustration of a smooth metal rod 4602 and a tube 4604of a heating chamber in accordance with one embodiment of the presentspecification. The rod 4602 is placed beside the tube 4604 in theapproximate axial position it occupies once inserted into the tube 4604for operation. In various embodiments, the tube 4604 has a lengthranging from 0.50 inches to 5.0 inches. In various embodiments, the tube4604 has an inner diameter ranging from 7/32 inches to 2.0 inches and anouter diameter ranging from ¼ inches to 2.5 inches. In one embodiment,the tube 4604 has a length of 3¼ inches, an inner diameter of 11/32 inchand an outer diameter of ½ inch. In various embodiments, the metal rod4602 has a length ranging from 0.4 to 5 inches and a diameter rangingfrom 5/32 inches to 2 inches. In one embodiment, the metal rod 4602 hasa length of 2 inches and a diameter of 5/16 inch. In one embodiment, themetal rod 4602 is composed of regular steel. In one embodiment, themetal rod 4602 has a surface area to volume ratio that is equal orgreater than 2(D₁+L)/D₂×L, where D₁ is the shortest cross-sectionaldimension of the metal rod 4602, D₂ is the longest cross-sectionaldimension of the metal rod, and L is the length of the metal rod. Invarious embodiments, the metal rod 4602 has a length less than 10 cmwith a smallest cross-sectional dimension of greater than 1 mm. In otherembodiments, the metal rod 4602 has a length greater than 1 mm and alargest cross-sectional dimension of less than 10 cm. In one embodiment,the metal rod 4602 has a length of 50.8 mm and a diameter of 7.94 mm. Invarious embodiments, the metal rod 4602 has a mass in a range between 1g and 100 g. In one embodiment, the metal rod 4602 has a mass of 19.8 g.

FIG. 46C is a flow chart illustrating the steps involved in generatingsteam 4628 using an induction heated metal core 4624, in accordance withone embodiment of the present specification. Power 4622 is delivered tothe system to cause an induction coil to heat the metal core 4624 asenergy per unit time or joules per second [J/sec]. Water 4626 is inputto the system having a flow rate F expressed in milliliters per minute[ml/min] at a room temperature T_(room) [° C.]. The system outputs steam4628 at a temperature T_(steam) [° C.]. In various embodiments, if flashheating is used to rapidly generate steam at start-up, the metal core4624, if pre-heated to more than 250° C., preferably possesses a thermalcapacity greater than or equal to the heat needed to vaporize 1 ml ofwater but less than the heat needed to vaporize 100 ml of water from 25°C. to 125° C. The thermal capacity of the metal core 4624, expressed incal/K, is a measure of how much energy the metal core 4624 can store inabsolute terms for a given temperature increase. Since the thermalcapacity is a measure of the absolute energy that can be stored in themetal core 4624, it scales approximately linearly with the mass of themetal core 4624 and the temperature of the metal core 4624 up to itsmelting point. Once the metal core 4624 has been pre-heated, forexample, to 250° C., room temperature water 4626 is passed over the core4624 and thermal energy is transferred from the core 4624 to the water4626. Depending on the amount of energy stored in the metal core 4624,the transferred energy first heats the water 4626, then boils it,evaporates it, and then overheats the generated steam 4628 to atemperature greater than 100° C. The pre-heated metal core 4624 releasesa certain amount of energy depending on how much it is allowed to coolas the stored thermal energy is transferred to the water 4626. The phaseof the water 4626 depends on the volume of water 4626 and the amount ofenergy transferred. The water 4626 undergoes an abrupt phase transitionbut the metal core 4624 does not. The absolute thermal capacity in cal/Kis for a given material and amount of said material and is differentfrom the specific heat capacity, expressed in cal/g*K normalized to aunit mass. The specific heat capacity defines the properties of amaterial independent of the amount of said material.

In various embodiments, the metal core 4624 possesses a thermal capacityranging from 0.05 cal/K to 1 Mcal/K and, more preferably, 640 cal/K to64 kcal/K. The metal core 4624 possesses a minimum required thermal massfor effective and consistent rapid heating of vapor. A higher thermalmass allows for more stable temperatures in the metal core 4624. Too lowof a thermal mass will result in fluctuating temperatures in the metalcore 4624. In various embodiments, the metal core 4624 is composed ofsteel. Steel has a specific thermal capacity of 0.12 cal/g*K. In anembodiment, a 100 g steel core undergoes a 100 K temperature drop whenits outer surface comes into contact with room temperature water. Thisreleases approximately 1,200 cal of thermal energy (100 g*100 K*0.12cal/g*K). Since water has a latent heat of vaporization of 543 cal/gm,approximately 2.2 ml of water can be vaporized using a 100 g steel core(1,200 cal/(543 cal/gm)) while its temperature drops 100K. This processuses a significant portion of the stored energy in the steel core andtherefore, to continue the flow of vapor, the steel core needs to bere-supplied with thermal energy via induction heating. When pre-heated,the metal core 4624 uses a portion of its stored thermal energy to heatand vaporize water once the water touches its outer surface. In variousembodiments, the metal core 4624 uses 1% to 100% of its stored thermalenergy to vaporize a given volume of water. Using a smaller amount ofthe stored thermal energy, for example, 10%, during vaporization allowsthe metal core 4624 to maintain a more consistent temperature andimproves system reliability.

In one embodiment, wherein the metal core 4624 comprises a steel rodhaving a length of 50.8 mm, a diameter of 7.94 mm, and a mass of 19.8 g,and water is supplied to the outer surface of the core 4624 at a rate of5 ml/min (5 g/60 sec), the system is expected to exhibit a plurality ofcharacteristics based on the following formulas.

The power (P_(boil)) needed to heat the water from room temperature (20°C.) to the boiling point (100° C.), a temperature difference of ΔT=80Kis:

$P_{boil} = {{{\frac{M}{t} \cdot c_{water} \cdot \Delta}\; T} = {\frac{5\mspace{14mu} {g \cdot 4.187}\mspace{14mu} {J \cdot 80}\mspace{14mu} K}{60\mspace{14mu} {\sec \cdot g \cdot K}} = {{27.9\frac{J}{\sec}} = {27.9\mspace{14mu} W}}}}$

where M is the mass of water in grams, t is time in seconds, andc_(water) is the specific heat capacity of water.

The power (P_(vap)) needed to vaporize the water at the boiling point(100° C.) into wet steam (100° C.) is:

$P_{vap} = {{{\frac{M}{t} \cdot \Delta}\; H_{vap}} = {\frac{5\mspace{14mu} {g \cdot 2270}\mspace{14mu} J}{60\mspace{14mu} {\sec \cdot g}} = {{189.2\frac{J}{\sec}} = {189.2\mspace{14mu} W}}}}$

where M is the mass of water in grams, t is time in seconds, andΔH_(vap) is the latent heat of vaporization of water.

The power (P_(steam100→250)) needed to heat wet steam (100° C.) tooverheated steam at 250° C., a temperature difference of ΔT=150K is:

$P_{{{steam}\; 100}\rightarrow 250} = {{{\frac{M}{t} \cdot c_{steam} \cdot \Delta}\; T} = {\frac{5\mspace{14mu} {g \cdot 1.996}\mspace{14mu} {J \cdot 150}\mspace{14mu} K}{60\mspace{14mu} {\sec \cdot g \cdot K}} = {{25.0\frac{J}{\sec}} = {25.0\mspace{14mu} W}}}}$

where M is the mass of water in grams, t is time in seconds, andc_(steam) is the specific heat capacity of steam.

The power (P_(water20→steam100)) needed to generate steady state wetsteam (100° C.) is:

P _(water20→steam100) =P _(boil) +P _(vap)=27.9 W+189.2 W=217.1 W

The power (P_(water20→steam250)) needed to generate steady stateoverheated steam at 250° C. is:

P _(water20→steam250) =P _(boil) +P _(vap) +P _(steam100→steam250)=27.9W+189.2 W+25.0 W=242.1 W

In one embodiment, with no water flow and assuming no heat loss, theenergy (ΔH_(20→250)) needed to heat the core 4624 from room temperature(20° C.) to 250° C. is:

${\Delta \; H_{20\rightarrow 250}} = {{{M \cdot c_{steel} \cdot \Delta}\; T} = {\frac{19.8\mspace{14mu} {g \cdot 0.486}\mspace{14mu} {J \cdot 230}\mspace{14mu} K}{g \cdot K} = {2213\mspace{14mu} J}}}$

where M is the mass of the core in grams, and c_(steel) is the specificheat capacity of steel.

The power needed to generate wet steam at a water flow rate of 5 ml/minfrom room temperature (20° C.) is calculated above to be 217.1 W. Ifthis power level is used to preheat the core 4624 with no water flow,then the core 4624 will be heated from 20° C. to 250° C. in the time(t_(preheat20→250)) of:

$t_{{{preheat}\; 20}\rightarrow 250} = {\frac{\Delta \; H_{20\rightarrow 250}}{P_{{{water}\; 20}\rightarrow{{steam}\; 100}}} = {\frac{2213\mspace{14mu} {J \cdot \sec}}{217.1\mspace{14mu} J} = {10.2\mspace{14mu} \sec}}}$

If the water flow rate is set to 5 ml/min and 242.1 W of power areprovided, the system will output overheated steam at a temperature of250° C. in a steady-state condition. If the overheated steam is directedtoward a heat-absorbing surface (target tissue at 37° C.), then thefollowing powers will be released to the surface.

Power (P_(steam100→250)) release from 250° C. overheated steam to wetsteam:

P_(steam100→250)=25.0 W, approximately 10.3% of the total power of 242.1W.

Power (P_(vap)) release from release of latent heat of vaporization, wetsteam to boiling water:

P_(vap)=189.2 W, approximately 78.2% of the total power of 242.1 W.

Remaining power (P_(water100→37)) released from boiling water as itcools to 37° C. in living tissue:

P_(water100→37)=22 W, approximately 9.1% of the total power of 242.1 W.

FIG. 46B is a top-down illustration of the metal rod 4602 positionedwithin the tube 4604 of the heating chamber 4600 of FIG. 46A. A space4603 is created between the inner surface 4604 a of the tube 4604 andthe outer surface 4602 a of the metal rod 4602. The space 4603 acts as apassage for the water as it travels between the tube 4604 and rod 4602and is converted to steam by heat transfer from the rod 4602 to thewater. In various embodiments, the width w of the space 4603 is nogreater than 25 mm. In one embodiment, the width w of the space 4603 is1 mm. In various embodiments, as water is pumped into the space 4603,the heating chamber is capable of creating steam and withstandingpressures between 1 and 100 PSI. In one embodiment, as water is pumpedinto the space 4603, the heating chamber is capable of creating steamand withstanding a pressure of at least 5 PSI. In various embodiments,water is pumped into the space 4603 at a flow rate of 0.1-100 ml/min.

During operation, the metal rod 4602 is heated via induction heatingsuch that the temperature at its outer surface 4602 a is at least 100°C. to convert water in the space 4603 to steam. The heat from the rod4602 is also sufficient to heat the inner surface 4604 a of the tube4604 to at least 100° C. to allow for the vapor conversion to occur. Invarious embodiments, the tube 4604 provides sufficient thermalinsulation such that its outer surface 4604 b has a temperature lessthan 100° C., and preferably, less than 60, 50, 40, 30, and 25° C., toallow safe handling by an operator. In various embodiments, thetemperature of the outer surface 4604 b of the tube 4604 of the heatingchamber does not increase by more than 500% of its pre-operation outersurface temperature during continuous operation time periods of 10, 9,8, 7, 6, 5, 4, 3, 2, or 1 minute down to 5 seconds and any time periodin between. In one embodiment, during continuous operation, atemperature of the ferromagnetic material of the heating chamber ismaintained at a level greater than 100° C. In one embodiment, thetemperature of the outer surface 4604 b of the tube 4604 of the heatingchamber does not increase by more than 500% of its pre-operation outersurface temperature during 5 minutes or less of continuous operation. Inone embodiment, the heating chamber 4600 includes a valve at an outletport that opens at pressures equal to or less than 5 atm. In oneembodiment, the heating chamber 4600 includes a valve at an inlet portthat allows backflow of the water at a pressure greater than 5 atm. Invarious embodiments, the ablation system further includes at least onecooling system to maintain the temperature of the outer surface 4604 bof the tube 4604 at the temperature ranges listed above. In oneembodiment, the heating chamber includes a mechanism positioned betweenthe outer surface 4604 b of the tube 4604 and an inner surface of theinduction coil for cooling said outer surface 4604 b. In one embodiment,the mechanism comprises a system for passing cooling fluid between saidsurface 4604 b and said coil. In another embodiment, wherein saidinduction coil is an induction chamber having a three-dimensional bodywith a lumen within and comprising said coils in the body of saidchamber, said induction chamber further comprises a cooling mechanismpositioned along an inner surface of said body. In one embodiment, thecooling mechanism comprises a system for passing cooling fluid betweensaid inner surface of said induction chamber body and said outer surface4604 b of said tube 4604. In one embodiment, a temperature of an outersurface 4604 b of the tube 4604 does not exceed 120° C. duringoperation. In another embodiment, a temperature of an outer surface 4604b of the tube 4604 does not exceed 150° C. during operation.

In various embodiments, the tube 4604 is composed of a thermallyinsulating material. In various embodiments, the tube 4604 is composedof a non-thermoplastic material. In one embodiment, the tube 4604 iscomposed of glass. In another embodiment, the tube 4604 is composed ofceramic. In one embodiment, the ceramic is a machinable glass such asMACOR®. In another embodiment, the tube 4604 is composed of athermoplastic. In one embodiment, the tube 4604 is composed of PEEK.Since PEEK has a melting temperature of 343° C., the temperature of theheating chamber, including the metal core, needs to be monitored so itdoes not approach high temperatures and melt the tube. In variousembodiments, the temperature of the metal rod 4602 is continuouslymonitored during operation to create a metal rod 4602 temperatureprofile. The maximum temperature in the temperature profile isidentified and the location of the maximum temperature in the metal rod4602 is also identified. The temperature distribution and maximumtemperature may change depending on the location of the boundary betweenwater and steam (where vapor conversion occurs). In various embodiments,the temperature profile includes an axial temperature distribution and aradial temperature distribution which may be different in space andtime. The radial temperature distribution is affected by volumetricheating and surface cooling of the rod 4602. In various embodiments, themetal rod 4602 is positioned in a vertical orientation and the maximumtemperature location is along a vertical axis of the rod 4602. Atemperature sensor, or thermocouple, is then positioned at the maximumtemperature location in the metal rod 4602 to ensure that, duringoperation, the highest temperatures encountered in the heating chambercan be monitored. Feedback from this thermocouple is then used toregulate system operation and provide system stability. In oneembodiment, a thermocouple is positioned within a central bore which isdrilled into said metal rod 4602 from its distal end. In one embodiment,the bore is drilled into said distal end a distance approximately equalto ⅓ of the length of the metal rod 4602. In one embodiment, the metalrod 4602 has a length of approximately 5 cm and a central bore isdrilled into the distal end of the rod 4602 to a distance ofapproximately 1.7 cm (approximately ⅓ of the total length of the rod4602). A thermocouple is positioned within the bore. In variousembodiments, the maximum temperature location in the metal rod 4602 iswithin 1 cm or more from the location of the thermocouple. In variousembodiments, the thermocouple is positioned at a location having atemperature within 70% of the maximum temperature. In variousembodiments, the thermocouple is positioned at a location that isapproximately 1.7 cm from the location of the maximum temperature. FIG.47 is an illustration of a distal end of a metal rod 4702 of a heatingchamber with a thermocouple 4706 positioned therein. In one embodiment,the highest temperatures of the metal rod 4702 are encountered at itsdistal end and so the thermocouple 4706 is positioned at that location.A small bore 4703 has been drilled into the distal end of the metal rod4702 to tightly fit the thermocouple 4706. In one embodiment, the end ofthe thermocouple 4706 is positioned ½ inch into the distal end of themetal rod 4702. Thermocouple 4706 is depicted as thermocouple 4034 inFIG. 40A and effectively regulates the temperature of the heatingchamber core, thereby allowing proper and safe operation of the ablationsystem.

Monitoring the temperature of the induction coil, along with monitoringthe temperature of the heating chamber core, is beneficial in providinga safe and properly functioning ablation system. In one embodiment, thehighest temperatures experienced by the coil are located along its firstlayer of windings against the tube of the heating chamber. The outerlayers of the coil are cooled by a fan, as described with reference toFIG. 40A. Cooling of the interior layers of the coil is inefficient, andtherefore temperatures at these layers must be monitored to preventdamage to the coil. FIG. 48A is an illustration of a tube 4804 of aheating chamber and a thermocouple sheath 4807 in accordance with oneembodiment of the present specification. The tube 4804 includes a cutout4809 to accommodate the thermocouple sheath 4807. The sheath 4807 ispartially inlaid into the outer surface of the tube 4804 such that itwill not significantly increase the outer profile of the tube 4804 andpush the coil inner diameter unnecessarily far from the heating chamber.In one embodiment, the sheath 4807 has a length that is sufficient toextend along the entire coil once the coil has been positioned about thetube 4804. The tip of a thermocouple can be repositioned anywhere alongthe length of the sheath 4807 to measure the axial temperaturedistribution of the interior of the induction coil. The thermocouplesheath 4807 is configured to house thermocouple 4036 depicted in FIG.40A. FIG. 48B is an illustration of the tube 4804 of FIG. 48A with thethermocouple sheath 4807 positioned within the cutout 4809. In oneembodiment, the temperature of the inner layers of the coil is monitoredto remain below 155° C. and prevent damage to the coil. In oneembodiment, the thermocouple sheath 4807 is composed of PEEK and has anouter diameter of 1/16 inch. In various embodiments, the sheath 4807 hasa length ranging from 1 to 3 inches. In various embodiments, the cutout4809 has a length equal to or greater than the length of the sheath 4807to allow for repositioning of the sheath 4807. In one embodiment, asmall infrared-transparent window insert into the PEEK heating chamberis created and an infrared sensor is used to measure the temperature ofthe core inside the PEEK heating chamber.

FIG. 48C is an illustration of the tube 4804 and thermocouple sheath4807 of FIG. 48B with first and second flanges 4811, 4813 positionedover said tube 4804 and sheath 4807 in accordance with one embodiment ofthe present specification. The flanges 4811, 4813 serve to limit theproximal and distal placement of the coil on the tube and, together withthe tube 4804, create a spool-like shape for the heating chamber. Thesheath 4807 extends the entire length of the spool, allowing the tip ofa thermocouple to probe the coil temperature at any axial position. Inone embodiment, the metal rod inside the heating chamber extendsslightly beyond the flanges 4811, 4813. FIG. 48D is an illustration ofthe tube 4804, sheath 4807, and flanges 4811, 4813 of FIG. 48C with athermal compound 4815 applied to the components in accordance with oneembodiment of the present specification. The thermal compound 4815 isapplied liberally to the thermocouple sheath 4807, under the first layerof coil windings, to facilitate good thermal contact between the sheath4807, tube 4804, and coil. In one embodiment, the thermal compound 4815is silicone-based.

FIG. 48E is an illustration of the tube 4804, sheath 4807, flanges 4811,4813, and thermal compound of FIG. 48D with an induction coil 4805wrapped about said tube 4804 and sheath 4807. In one embodiment, thecoil 4805 comprises 1,200-strand litz wire with each AWG-46 strandhaving a thickness of 42 μm. In one embodiment, each strand is coatedwith a thin insulating layer of polyester or polyurethane according tothe NE-F1 Class F Electrical Insulation System and has a maximum workingtemperature of 155° C. In various embodiments, the coil 4805 is spacedapart from the outer surface of the tube 4804 by at least 0.1 mm. In oneembodiment, during operation, the outer surface of the tube 4804 isconfigured to be heated to a temperature at least 20° C. below atemperature of the inner surface of the tube 4804. In one embodiment, acooling agent is passed between the coil 4805 and the tube 4804 tomaintain the temperature of the outer surface of the tube 4804 below100° C. In another embodiment, a cooling agent is passed between thecoil 4805 and the tube 4804 to maintain the temperature of the outersurface of the tube 4804 at a temperature which is at least 20° C. lessthan the temperature of an inner surface of the tube 4804. In oneembodiment, during operation, the system is programmed to shut downheating when the outer surface of the tube 4804 is heated to atemperature greater than 100° C.

In one embodiment, an ablation system of the present specificationincludes a manifold configured to route the leads of the thermocouplefitted in the metal core to the system electronics. The manifold isconfigured to route the leads without causing a leak or a short circuit.FIG. 49A is an illustration of the distal end of a heating chamber 4900depicting a lead 4917 of a thermocouple 4907 positioned within the metalcore 4902 of the chamber in accordance with one embodiment of thepresent specification. The distal flange 4913 of the heating chamber4900 is also shown. Another lead (not shown) extends distally from thethermocouple 4907. The leads of the thermocouple 4907 are in the fluidpathway and must be routed out of said pathway and to the systemelectronics. The lead 4917 depicted in FIG. 49 is insulated to avoidcontacting and short circuiting with the other lead (not shown) of thethermocouple 4907. In one embodiment, the insulation is a fiberglasssheath. Contact and short circuit of the leads would in essence move thesensitive thermoelectric junction to the point of the short circuit.Therefore, one lead is insulated to prevent short circuiting.

FIG. 49B is an illustration of a manifold 4950 configured to route theleads of a heating core thermocouple in accordance with one embodimentof the present specification. In one embodiment, the manifold 4950 has athree-dimensional “cross” shape including a proximal section 4951, adistal section 4952, a left section 4953, and a right section (notshown), all extending outwardly from a center section 4955 of the cross.The interiors of the proximal section 4951 and distal section 4952 arein fluid communication with one another through the interior of thecenter section 4955. The interiors of the left section 4953 and rightsection (not shown) are configured to receive a compression seal and acompression screw as described below. In one embodiment, the manifold4950 is composed of PEEK. The proximal section 4951 includes an openingfitted with a first connecting mechanism at its proximal end. The firstconnecting mechanism is configured to couple with an adapter 4925 which,in turn, in configured to couple to the distal end of the tube 4904 ofthe heating chamber 4900, fixedly securing the manifold 4950 to theheating chamber 4900. In one embodiment, the first connecting mechanismof the proximal section 4951 is a female ⅛″-27 NPT coupling and theadapter 4925 is a ⅛″-27 NPT male-male brass nipple.

The left section 4953 includes an opening 4963 at an end facing oppositeto said center section. The opening 4953 enters into the interior of theleft section 4953 which is in fluid communication with the interior ofthe center section 4955. The leads of a thermocouple fitted into thedistal end of a metal heating core of the heating chamber 4900 aredirected through the distal end of the tube 4904, through the adapter4925, and into the interior of the proximal section 4951 of the manifold4955 through the opening at the proximal end of said proximal section4951. The leads pass through the interior of the center section 4955 andthen one lead is directed through the interior of the left section 4953while the other lead is passed through the interior of the right section(not shown). Referring to FIG. 49B, a lead 4927 is depicted extendingout of the opening 4963 of the left section 4953. The other lead extendsout of a similar opening on the right section of the manifold 4950. Acompression seal 4965 and a compression screw 4967 are configured to fitsecurely into the interior of the left section 4953. The compressionseal 4965 is inserted first and acts to seal the interior of the leftsection 4953 from the interior of the center section 4955 and thus theinteriors of the proximal section 4951 and distal section 4952. Thecompression screw 4967 is screwed into the interior of the left section4953 after the seal 4965 has been placed into position. An interiorsurface of the interior of the left section 4953 includes a thread forreceiving the compression screw 4967. Small holes are bored through thecenter of the compression seal 4965 and compression screw 4967 forpassage of the lead 4927. The lead 4927 fits snugly within said holes toprevent leaking. The lead 4927 then extends beyond the compression screw4967 and to the system electronics. In one embodiment, compression seal4965 is composed of high-temperature silicone rubber. In one embodiment,the compression seal 4965 has a thickness of 1/32 inch. In oneembodiment, the compression screw 4967 is a drilled-out ¼″-28 NFall-thread and the left section 4953 comprises a compression fittingfeed-through with ¼″-28 NF threads for receiving the compression screw4967. The right section (not shown) functions in the same manner to theleft section 4953 and includes another compression seal and compressionscrew for passage of the other lead.

FIG. 49C is an illustration of the manifold 4950 of FIG. 49B with acompression screw 4967 positioned in the left section 4953. One of theleads 4927 from the thermocouple fitted into the metal core of theheating chamber 4900 is depicted exiting the manifold 4950 through thecompression screw 4967 in the left section 4953. Another lead 4917 isdepicted extending from the right section 4954 on the opposite side ofthe manifold 4950. The manifold 4950 allows for safe routing of theleads 4917, 4927 from the heating chamber metal core thermocouple, outof the fluid pathway, and to the system electronics. FIG. 49D is atop-down illustration of the manifold 4950 of FIG. 49C depicting theroutes taken by the thermocouple leads 4917, 4927 within the manifold4950 as they exit the fluid pathway. The interior of the manifold 4950is visible through an opening 4959 at the distal end of said manifold4950. Lead 4917 is depicted with an insulating sheath within themanifold 4950 and extends upward from the interior of the proximalsection of the manifold 4950, turns into the feed-through of the rightsection 4954, and exits the manifold 4950 through a compression screw4957 fitted into said right section 4954. Lead 4927 is depicted withinthe manifold 4950 and extends upward from the interior of the proximalsection of the manifold 4950, turns into the feed-through of the leftsection 4953, and exits the manifold 4950 through a compression screw4967 fitted into said left section 4953.

FIG. 49E is an illustration of the manifold 4950 of FIG. 49D with a luerlock connector 4970 attached to the distal end of the manifold 4950. Theluer lock connector 4970 functions as a steam port for the attachment ofa catheter. The luer lock connector 4970 attaches to the distal section4952 of the manifold at opening 4959 shown in FIG. 49D. The lumen of theheating chamber 4900 is in fluid communication with the interior of themanifold 4950, which in turn, is in fluid communication with the luerlock connector 4970. In one embodiment, the luer lock connector 4970 iscomposed of metal. In one embodiment, the metal luer lock 4970 and metaladapter 4925 draw heat away from the steam as they are better heatconductors than the PEEK of the manifold 4950. Therefore, in oneembodiment, as depicted in FIG. 49F, the metal luer lock 4970 and metaladapter are wrapped in a thermally insulating material 4973, 4974,respectively. In one embodiment, the thermally insulating material 4973,4974 is black thermal insulation tape. FIG. 49F also depicts the leads4977 of an additional thermocouple positioned proximate the adapterconnecting the heating chamber 4904 and the manifold 4950. Thisthermocouple measures the temperature just outside adapter which isclosest to the temperature of the steam entering the proximal end of acatheter 4979 attached to the luer lock 4970. This thermocouple isdepicted as thermocouple 4032 in FIG. 40A and effectively regulates thetemperature of steam exiting the heating chamber, thereby providing theoperator with sufficiently heated vapor for ablation. The adapter is notvisible in FIG. 49F, as the adapter and said additional thermocouple arecovered by insulating material 4974. In one embodiment, the entiremanifold is then encapsulated in shrink tubing for additionalinsulation, as depicted with reference to manifold 4148 in FIG. 41C. Inone embodiment, the shrink tubing is black polyolefin shrink tubing.

As discussed with reference to FIG. 40A, in one embodiment, an ablationsystem of the present specification includes three thermocouples. Afirst thermocouple is positioned distal to the heating chamber to sensethe temperature of steam generated by said heating chamber. A secondthermocouple is fitted into the distal end of the metal core of theheating chamber to monitor the hottest portion of said heating chamber.A third thermocouple is positioned between the tube of the heatingchamber and the induction coil to ensure the coil is not damaged by hightemperatures. FIG. 49G is a schematic diagram of a thermocouple analogfront end in accordance with one embodiment of the presentspecification. The hot junction 4932 is placed at the point wheretemperature is to be measured and the cold junction 4934 is connected toterminal block 4147 of FIG. 41C. In one embodiment, the system includesa cold junction compensation circuit. To minimize noise pickup by thethermocouples, the analog front end electronics of the thermocouples aredesigned with operational amplifiers in differential mode. Any noisecoupled to the leads of the thermocouples is rejected as common-modesignal. Noise generated between the leads is mainly shorted out by thevery low impedance of the thermocouple junction, assuring maximum noiserejection. To further reduce noise pickup, the analog front endelectronics are located as close as possible to the thermocouple hotjunctions. Referring again to FIG. 41C, in one embodiment, the systemincludes a steel shielding box 4145 containing the analog front endelectronics of the thermocouples. The steel shielding box 4145 ispositioned proximate the hot junctions which, as described above, arepositioned just distal to the heating chamber 4104 under the thermallyinsulating material covering the manifold 4148, in the metal core of theheating chamber 4104, and under the induction coil 4105.

In various embodiments, one or more temperature sensors, orthermocouples, as described above, are used to regulate functionality ofthe vapor ablation system. Information sensed and relayed by thethermocouple(s) provides active and consistent temperature sensorreadings to determine the stability of the system. Once a safe operatingtemperature, signifying system stability, has been sensed, the systemthen permits the user to proceed to the next step and generate steam forablation. In various embodiments, the system allows for a higher maximumcurrent to be provided to the induction coil, thereby increasing systemresponsiveness during steam delivery. In addition, in variousembodiments, the treatment temperature, or steam temperature, is high(>100° C.) to improve steam generation efficiency. A microcontroller,comprising a portion of the data acquisition and control electronics4024 of FIG. 40A, controls system temperatures based on sensed data fromthe thermocouple(s) and prevents temperature overshoot. In someembodiments, the microcontroller employs aproportional-integral-differential algorithm in a control loop feedbackmechanism to control the core temperature. The microcontrollercalculates an error value as the difference between the measuredtemperature and a pre-determined target treatment temperature and thenminimizes the error by adjusting the process through the use of amanipulated variable. In some embodiments, steam temperature is alsocontrolled by setting a taper temperature, as described with referenceto FIG. 52 below. In one embodiment, setting a lower taper temperatureprovides increased control over steam temperature.

FIG. 49H is a flowchart listing the steps involved in regulating steamtemperature and vapor ablation system stability, in accordance with oneembodiment of the present specification. At step 4935, electrical energyis provided to an induction coil, resulting in induction heating of aheating chamber core and pre-heating of the core to a pre-determinedtemperature suitable for treatment. In various embodiments, thetemperature suitable for treatment includes a range of stabletemperatures sufficient for steam generation yet still low enough toprevent injury to the user or patient or damage to the system. Invarious embodiments, the temperature range is 100 to 300° C. In oneembodiment, a sensed temperature is considered stable by the system, andsteam generation is allowed to occur, when the sensed temperature iswithin +/−5% of a target temperature. At least one thermocouplecontinuously senses the temperature of the core at step 4936. Once thecore temperature reaches the pre-determined temperature suitable fortreatment at step 4937, the system permits the user to begin steamgeneration. In various embodiments, the system notifies that the desiredcore temperature has been reached, signifying the system is stable, byilluminating a “Core Ready” light on a graphical user interface (GUI) asdescribed below with reference to FIG. 52. In various embodiments, theuser can then generate steam and begin treatment by pressing a “DeliverRx” button on the GUI as described below with reference to FIG. 55 or,optionally, press a foot switch to generate steam and begin treatment.Steam generation commences when water is introduced into the heatingchamber by a pump at step 4938. Steam is then generated and delivered totarget tissues for ablation treatment at step 4939. In variousembodiments, energy delivery and thus steam generation ceases if thesensed core temperature rises above the pre-determined temperaturesuitable for treatment at step 4940. Once the core temperature fallsbelow the pre-determined temperature suitable for treatment as sensed bythe at least one thermocouple, steam generation and treatment mayresume.

In another embodiment, the temperature of the chamber or the coil can beused to drive the therapeutic regimen.

FIG. 49I is a block diagram illustrating a vapor ablation kit 4980comprising a handheld induction heating mechanism 4982 in accordancewith one embodiment of the present specification. The kit comprises aclosed water system which includes a water reservoir 4981 connected to ahandheld induction heating chamber 4982 which is in turn connected to acatheter 4983. The kit is considered a closed water system as there areno parts of the system which touch the water and are not sterile. Thecatheter 4983, examples of which are presented above, is single use anddisposable. The induction heating chamber 4982 and water reservoir 4982are preferably disposable but, in another embodiment, could also bereused. This embodiment improves the efficacy of steam delivery bygenerating the steam closer to the target. In various embodiments, thekit 4980 includes at least one sensor for monitoring operationalparameters of the kit 4980.

In another embodiment, the catheter includes a handle and the inductionheating mechanism is not housed in the handle to improve operatorsafety. Since heating does not occur in the handle, the handle is safefor the operator to touch. In other embodiments, additional heatingmechanisms can be deployed along the length of the catheter. Theseheating mechanisms could be used in various combinations for the idealcombination of safety, efficacy and reliability.

FIG. 49J is an illustration of a vapor ablation kit 4985 comprising awater reservoir 4986, heating chamber 4987, and catheter 4988, inaccordance with another embodiment of the present specification. The kit4985 also includes a handle 4989 for manipulating the catheter 4988. Thekit is considered a closed water system as there are no parts of thesystem which touch the water and are not sterile. This embodiment alsoimproves the efficacy of steam delivery by generating the steam closerto the target. In various embodiments, all components of the kit 4985are single use and disposable. The heating chamber 4987 is positionedwithin a separate induction coil (not shown) controlled by amicroprocessor. The water reservoir 4986, heating chamber 4987, catheter4988, and handle 4989 are considered a ‘catheter component’ and theinduction coil and microprocessor are considered a ‘generatorcomponent’. In other embodiments, the catheter 4988 and handle 4989 aresingle use and disposable while the water reservoir 4986 and heatingchamber 4987 can be reused. In some embodiments, the kit 4985 includesat least one sensor for monitoring operational parameters of the kit4985.

FIG. 49K is a vertical cross section illustration of an inductionheating chamber 4901 in accordance with one embodiment of the presentspecification and FIG. 49L is an illustration of the induction heatingchamber of FIG. 49K depicting the various components of the chamber infurther detail. Referring to FIGS. 49K and 49L simultaneously, theheating chamber 4901 includes a ferromagnetic core 4903 contained withina non-ferromagnetic housing or thermoplastic container 4905. Thethermoplastic container 4905 includes an inlet port 4906 at its proximalend and an outlet port 4908 at its distal end. An induction coil 4909 iswound about the thermoplastic container 4905. A first portion ofnon-thermoplastic insulation 4910 is positioned within the thermoplasticcontainer 4905 and between the walls of the thermoplastic container 4905and the ferromagnetic core 4903. A second portion of non-thermoplasticinsulation 4911 is positioned between the walls of the thermoplasticcontainer 4905 and the induction coil 4909.

In some embodiments, the thermoplastic container 4905 has a lengthranging from 2.75 inches to 3.75 inches, an inner diameter ranging from7/32 inches to 11/32 inches, and an outer diameter ranging from ⅜ inchesto 0.5 inches. In some embodiments, the ferromagnetic core 4903 has alength ranging from 1.5 inches to 2.5 inches and a diameter ranging from3/16 inches to 5/16 inches.

In various embodiments, the thermoplastic container 4905 is composed ofPEEK, ABS, acetal, polyamide, or polyvinylidene difluoride (PVDF). Insome embodiments, the first portion of non-thermoplastic insulation 4910comprises a film of mica rolled to create a stand-off within theproximal end and distal end of the thermoplastic container 4905 toprevent the ferromagnetic core 4903 from contacting the PEEK. An outerperimeter of the mica roll also extends along the length within thethermoplastic container 4905 to prevent the ferromagnetic core fromcontacting the PEEK walls. A pair of central openings 4912, 4914 arepositioned in the proximal and distal ends of the mica rollrespectively, to allow water to flow into a space between the mica rollsand the ferromagnetic core 4903. In some embodiments, the ferromagneticcore 4903 is a unitary member and includes grooves 4998 encircling itsouter periphery. The grooves 4998 are configured to allow water or steamto flow along the core 4903. In an embodiment, the ferromagnetic core4903 includes grooves or notches 4915 formed into its proximal end anddistal end creating channels for water or steam to flow between the core4903 and surrounding insulation 4910. In another embodiment, theproximal and distal ends of the ferromagnetic core are flat and theinsulation 4910 includes grooves or notches formed into its surfacescontacting the proximal and distal ends of the ferromagnetic core tocreate channels for water and steam flow.

FIG. 49M is a horizontal cross section illustration of the inductionheating chamber 4901 of FIG. 49K. The induction heating chamber 4901includes a ferromagnetic core 4903 surrounded by a first portion ofnon-thermoplastic insulation 4910 which is surrounded by a thermoplasticcontainer 4905 which, in turn, is surrounded by a second portion ofnon-thermoplastic insulation 4911. An induction coil 4909 is wound aboutthe second portion of non-thermoplastic insulation 4911. In anembodiment, the ferromagnetic core 4903 is shaped such that a pluralityof channels 4999 are formed along its outer surface to allow for theflow of water or steam in a proximal to distal direction between theferromagnetic core 4903 and the first portion of non-thermoplasticinsulation 4910.

FIG. 49N is an illustration of a vapor delivery system 4920 including atleast one sensor 4928 for use with an endoscope 4930, in accordance withone embodiment of the present specification. The system includes acatheter 4921, a heating chamber 4922 with coil, connector 4924 forconnecting the coil to a generator, and fluid channel 4923 for supplyingfluid from a fluid source 4926. The system 4920 includes a first sensor4928 on the catheter 4921 that couples with an endoscope channel 4931 onthe endoscope handle 4933 and is configured to confirm the catheter 4921has been completely inserted into the endoscope channel 4931 by sendinga signal to the generator. Optionally, in an embodiment, the system 4920includes a locking mechanism to lock the catheter 4921 to the endoscopechannel 4931 to prevent inadvertent slippage of the catheter 4921 out ofthe endoscope channel 4931. Optionally, a second sensor 4929 attached tothe endoscope channel 4931 communicates with the sensor 4928 in thecatheter 4921 to confirm proper catheter 4921 positioning. In anembodiment, a compressible sheath 4919 covering the catheter 4921between the first sensor 4928 and the attachment 4924 to the generatoris included for providing additional insulation to the catheter 4921outside the endoscope 4930. The sheath 4919 is compressible and/orstretchable, allowing for insertion and withdrawal of the catheter 4921in and out of the endoscope channel 4931 with the insulated sheath 4919attached to the endoscope 4930. In an embodiment, this is achieved byhaving the insulated sheath 4919 composed of a stretchable material orhaving a corrugated design. In another embodiment, the sheath 4919 isnot attached to the catheter 4921 where it connects to the heatingchamber 4922, allowing the sheath 4919 to slide back and forth. In anembodiment, first sensor 4928 further includes an optional temperaturesensor for informing the user when the catheter 4921 temperature hasdecreased sufficiently to safely withdraw the catheter 4921 from theendoscope channel 4931. In various embodiments, the catheter includesinflatable balloons 4916, 4918 at its distal end for measuring bodycavity dimensions and occluding body cavity orifices as described in thepresent specification.

FIG. 49O is a flowchart illustrating the steps involved in oneembodiment of a method of delivering vapor ablation therapy using acatheter with a coil in the generator. In some embodiments, the catheteris similar to the catheter described with reference to FIG. 49N. At step4941, sterile packaging containing the catheter is opened. The catheteris removed and inserted into a catheter port on a generator at step4942. A water reservoir on the catheter is couple with a water pump, oneor more balloon ports are coupled with air pumps, and the heatingchamber is coupled with an RF coil at step 4943. At step 4944, thecatheter is locked into the generator using one or more lockingmechanisms. The catheter is inserted into an endoscope channel and thedelivery ports and balloons of the catheter are positioned proximate atarget tissue at step 4945. The dimensions of the tissue are measuredand input into the generator at step 4946. At step 4947, an ablativedose is calculated and treatment is initiated with vapor delivered per atreatment protocol. Optional sensors monitor therapy at step 4948. Aftertherapy, at step 4949, the catheter unlocks and slides out of thegenerator. At step 4956, a sensor in the catheter alerts the user whenit is safe to remove the catheter and optionally controls the catheterlocking mechanism. The catheter is removed from the generator anddiscarded at step 4958.

FIG. 49P is a flowchart illustrating the steps involved in oneembodiment of a method of delivering vapor ablation therapy using acatheter with a coil in the handle. In some embodiments, the catheter issimilar to the catheter described with reference to FIG. 49N. In oneembodiment, the heating chamber and coupled RF coil are in the handle.At step 4960, sterile packaging containing the catheter is opened. Thecatheter is removed and inserted into a catheter port on a generator atstep 4961. A water reservoir on the catheter is couple with a waterpump, one or more balloon ports are coupled with air pumps, and an RFelectric cord is connected to the generator at step 4962. At step 4964,the catheter is locked into the generator using one or more lockingmechanisms. The catheter is inserted into an endoscope channel and thecatheter handle locks into an endoscope accessory port at step 4966.Delivery ports and balloons of the catheter are positioned proximate atarget tissue at step 4968. The catheter can be moved in and out of theendoscope channel with the handle locked into the endoscope accessoryport for positioning. The dimensions of the tissue are measured andinput into the generator at step 4969. At step 4971, an ablative dose iscalculated and treatment is initiated with vapor delivered per atreatment protocol. Optional sensors monitor therapy at step 4972. Aftertherapy, at step 4975, the catheter unlocks and slides out of thegenerator. At step 4976, a sensor in the catheter alerts the user whenit is safe to remove the catheter and optionally controls the catheterlocking mechanism. The catheter is removed from the generator anddiscarded at step 4978.

FIG. 49Q is a flowchart illustrating the steps involved in oneembodiment of a method of using inflatable balloons of a vapor ablationcatheter to determine ablation dose. In some embodiments, the catheteris similar to the catheter described with reference to FIG. 49N. At step4990, the distal end of the catheter is passed through the distal tip ofan endoscope positioned in proximity to a target tissue. One or moreballoons are inflated to a first volume or a first pressure to measurethe dimensions of an organ at step 4991. The measured dimensions areinput into a generator at step 4992. At step 4993, optional informationon the target disease, indication, and patient is entered into thegenerator and a treatment regimen and ablation dose are calculated. Theone or more balloons are inflated to a second volume or a secondpressure to occlude the lumen of the organ and treatment is delivered atstep 4994. The one or more balloons are deflated and the catheter isremoved at step 4995.

System Software

The control of steam generation may be separated into low-level andhigh-level control. The low-level control involves fast feedback loopsof sensors and actuators with time constraints in the millisecond range.Examples include temperature control, power control, water flow control,and air flow control. Data acquisition and signal conditioning are alsoparts of the low-level architecture and serve as real-time monitoringfeatures to provide status information and feed safety shutdownalgorithms. In one embodiment, the low-level functions are controlled byan Arduino Due board with an Atmel ARM Cortex M3 microcontroller runningat 84 MHz clock speed. The difference between a microcontroller and amicroprocessor is that the microcontroller is a system-on-a-chip (SoC)having a CPU integrated with other computer peripherals. Amicrocontroller does not require an operating system in the conventionalsense, does not undergo a boot process, and runs in an endless loop assoon as power is applied. A microprocessor is a powerful CPU thatrequires external peripherals for its operation. The system thenrequires an operating system to coordinate the CPU with its peripherals,constituting a computer in the traditional sense. A boot process isrequired to load the operating system.

The high-level control is designed for user interaction through agraphical user interface. In an embodiment, the high-level control isfacilitated by a Raspberry Pi2 board, a computer with a Broadcom BCM2836SoC having a quad-core ARM Cortex-A7 CPU, a VideoCore IV dual-core GPU,and 1 GB of RAM integrated running at 900 MHz clock speed. For massstorage, the board requires an external MicroSDHC card essentiallyacting as a solid-state disk. In an embodiment, a capacitivetouch-screen is used as an input/output device for user interface. In anembodiment, the touch-screen is a 7 inch touch-screen. A user may inputthe desired steam generation without having to know or control any ofthe functions necessary to deliver the steam. In an embodiment, thehigh-level board and the low-level microcontroller are in direct two-waycommunication via a USB2 connection. In an embodiment, an externalcomputer may be connected to an Ethernet connector on the high-levelboard for remote maintenance or diagnostics.

For programming, the low-level microcontroller board requires a firmwareto be downloaded to be operable. The firmware is developed in anintegrated development environment (IDE). The IDE integrates compilers,linkers, libraries, and editors to build executable binary files thatmay be downloaded into the microcontroller's flash memory. In variousembodiments, the IDE comprises an Open-Source software package to avoidprogramming obstacles encountered with proprietary software systems.

As discussed with reference to FIG. 40A, the controller unit withgraphical user interface (GUI) controls a plurality of subsystems andtherefore key system parameters of the hardware of the ablation system.In one embodiment, the controller unit comprises a tablet PC and the GUIcomprises the tablet touchscreen. The GUI functions as the centralinteracting point of the user with the steam generator. The GUI must beon and running properly to fully and safely control the operation of theablation system. Therefore, in one embodiment, the GUI is powered onbefore the main power switch (switch 4114 of FIG. 41B) of the inductionheater electronics is turned on at the front panel of the enclosure. Inone embodiment, shutting the system down is accomplished by firstdisabling the heater and pump on the GUI, then switching off the mainpower switch, and finally shutting down the GUI.

The GUI controls the parameters of the ablation system and acquires datacontinuously at approximately 2 Hz or two samples per second. In variousembodiments, the GUI displays these parameters in charts, on indicators,buttons, dials, and lights and sounds an acoustic alarm if triggered. Inone embodiment, the GUI is configured to write all key system parametersto disk for later off-line data analysis. In one embodiment, the GUIoffers the programming of three distinct programs for generating steam.These programs are saved to disk so they will be available after the GUIhas been shut down. The programs can be loaded and automatically run thesteam generator according to the program sequence.

FIG. 50 is a screenshot of a graphical user interface (GUI) home screenin accordance with one embodiment of the present specification. A tablabeled “Home” 5050 has been pressed to display said home screen. TheGUI includes two distinct sections of common controls and indicators5001 at the top and the tab control 5020 occupying the lower mainsection. The common controls 5001 are relevant to all tabs and can beseen at all times, regardless of which tab is pressed. Each tab has itsown “theme” and is organized according to functional relation. Each tabis meant to convey the most pertinent information related to thedescriptive topic of the tab label. In one embodiment, the tabs arearranged from left to right in the natural sequence of progression ofthe system data flow. To begin using the GUI and ablation system, a userstarts the GUI loop by pressing the Pump/Heater Control button 5002. Alight 5003 illuminates and/or flashes to notify the user that the GUIloop is running properly. The user then switches on the main powerswitch on the induction heater. The GUI will then begin to displaysystem data and is ready to accept operator control. To shut down theGUI and ablation system, the user first pushes the Enable Pump button5004 and Enable Heater button 5005 until each button reads “Disabled”.The user then switches off the main power switch on the inductionheater. The user then stops the GUI loop by pressing the Pump/HeaterControl button 5002. The light 5003 will then go dark. Finally, the userpresses the STOP button 5022 to stop the GUI and release deviceresources for the next launch of the GUI.

The common controls 5001 include up and down arrows for adjusting thepump flow rate 5007. The pump does not start until the Enable Pumpbutton 5004 is pressed so that flow rate can be set before the pump isenabled. The common controls also includes up and down arrows foradjusting the heater current 5010. Adjusting the heater current sets thetiming of the phase control electronics that controls the AC powerdelivered to the induction heater electronics. This current is notcalibrated but is independently measured with the current-sensingcircuitry. The heater does not start heating until the Enable Heaterbutton 5005 is pressed so that the current can be set before the heateris enabled. The GUI is configured to log data of key parameters andwrite them to a file on the hard disk. The controls are available in aData Logging section 5015 in the common controls 5001.

The GUI continuously checks critical parameters of the system, such astemperatures, pressure and water level. If any of these parametersexceed pre-set values, then an alarm will be audio-visually activatedand the GUI will respond according to the particular alarm flag set. Inone embodiment, the common controls 5001 include a Systems Alarmssection 5030. If the core temperature exceeds 300° C. a “Temp.>300 C ?”button 5031 will change its text from “Temp. OK” to “Too High”, itscolor will change to red, a warning message will be displayed, theheater will be turned off and the pump will be turned on for emergencycooling. In one embodiment, this emergency shutdown will not stop whenthe core temperature has dropped to safe levels, but rather the operatormust check the system and take appropriate action. If the pressureexceeds 25 PSI the “Press.>25 PSI ?” button 5032 will change its textfrom “Pressure OK” to “Too High”, its color will change to red, awarning message will be displayed and the heater and pump will both beturned off. In one embodiment, after a pressure shutdown, the operatormust check the system and find out what caused the pressure to becomeexcessive. Excessive pressure indicates a problem in the plumbingsystem, most likely a blockage that must be removed before normaloperation can resume. If the water level in the water reservoir dropsbelow approximately ⅓ the capacity of the reservoir, then the “WaterLow?” button 5033 will change its text from “Level OK” to “Too Low” andits color will change to red. Because a low water level is not an acuteemergency, the GUI will continue normal operation. However, the operatoris advised to refill the water reservoir as soon as possible to assurenormal operation and to prevent running the pump dry. Once a sufficientwater level is reached the “Water Low?” button 5033 will change its textfrom “Too Low” to “Level OK” and its color will change to light gray. Inone embodiment, the user can press and hold the “Alarm Check” button5034 to check the proper functioning of the alarm indicators and theacoustic signals.

In one embodiment, the home screen includes at least one counter thatserves as a diagnostic tool to monitor the loop characteristics of theGUI. The home screen depicted in FIG. 50 includes a Block Diagram Count5052, a Master Loop Count 5054, a Loop 1 Count 5056, and a Loop 2 Count5058. The GUI is programmed in multi-threaded architecture so thatseveral tasks may be performed seemingly simultaneously in an apparentparallel fashion. This programming architecture has the advantage thatno one loop forces another loop to wait for it to be finished. Thisoffers great flexibility for the programmer and agility for the runningGUI.

FIG. 51 is a screenshot of a graphical user interface (GUI) systemstatus screen in accordance with one embodiment of the presentspecification. The GUI is programmed in an architecture that handles anumber of threads and subroutines, each performing a dedicated task. The“System Status” screen (displayed by the user pressing the System Statustab 5150) contains a number of resource and error indicators whichprovide an overview of the entire system and ensure the properfunctioning of all important software components. For example, theSystem Status screen displays the functional status for themicrocontroller (Arduino) 5152, thermocouples 5154, file writing 5156,and read/write Rx config 5158. A green check mark 5155 indicatesproblem-free operation while a red cross 5159 is an error flag that mustbe addressed and its problem corrected before the GUI can properlyfunction.

FIG. 52 is a screenshot of a graphical user interface (GUI) flow, heat,temps screen in accordance with one embodiment of the presentspecification. The “Flow, Heat, Temps” screen is accessed by pressingthe Flow, Heat, Temps tab 5250 and displays charts 5252, 5254 of pumpflow rate, heater current (set and actual) and thermocoupletemperatures. These charts 5252, 5254 begin to progress as soon as theGUI loop is started by pressing the Pump/Heater Control button 5202. Thescreen also includes legends 5256, 5258 of the various chartedparameters along with their displayed numeric values.

A Preheat Core button 5211 included in the common controls 5201initiates a closed control loop that thermostatically regulates thetemperature of the heater core and attempts to maintain its temperatureat a selected core temperature. The selected core temperature can be setby using up and down arrows to adjust the Core Temp 5212. The closedcontrol loop functions by considering a “Taper Temp. (° C.)” 5213 (alsoadjustable using up and down arrows) to prevent temperature overshootswhen a high heater power is selected. When the actual core temperature,as indicated by “Temp. Core (° C.)” 5259 in the temperature chart, isbelow the taper temperature, then the full heater power is applied torapidly heat the core and the “Heater Current (V)” 5210 is automaticallyset to its maximum value of 5.0 V. As the taper temperature is exceeded,the heater current will be set lower according to a linear relationshipbetween the selected “Core Temp. (° C.)” 5212 and “Taper Temp. (° C.)”5213. When the measured core temperature 5259 has reached the set “CoreTemp. (° C.)” 5212, the “Heater Current (V)” 5210 is set to 2.0 V, thelowest programmed value in this tapering scheme. If the measured coretemperature 5259 exceeds the set “Core Temp. (° C.)” 5212, then theEnable Heater button 5205 will be turned off and heating ceases. As themeasured core temperature 5259 cools below the set “Core Temp. (° C.)”5212, the regulating loop responds according to the actual coretemperature. A light labeled “Core Ready” 5214 illuminates when the corehas reached its set temperature. In one embodiment, a user can runtrials to find the optimal setting for “Core Temp. (° C.)” 5212 and“Taper Temp. (° C.)” 5213 to produce the most steam with the smallesttemperature overshoots for stable and continuous steam generation.

In one embodiment, the GUI includes chart controls 5222, 5224, 5226 tothe right of the tab control section 5220. The chart controls 5222,5224, 5226 are configured to affect all charts. The “Reset” button 5222resets all charts and uses an auto-scale feature to set the Y-axis tothe best range for visualization of the parameters. The “Chart HistorySize” 5224 is adjustable using up and down arrows and indicates howlarge a buffer the GUI will reserve to display data points of the chartsand how far back in time scrolling is possible. “Time Span” 5226 is alsoadjustable using up and down arrows and controls how many data pointswill be displayed in the current charts. This number can be changedwithout loss of data in the buffer.

FIG. 53 is a screenshot of a graphical user interface (GUI) heat,pressure screen in accordance with one embodiment of the presentspecification. The “Heat, Pressure” screen is accessed by pressing theHeat, Pressure tab 5350 and is similar in layout and function as the“Flow, Heat, Temps” screen described above. The parameters charted anddisplayed are the “Set Heater Current”, the “Actual Heater Power (W)”5352 as calculated from the measured current and the “Chamber InletPressure” 5354. The screen also includes legends 5356, 5358 of thevarious charted parameters along with their displayed numeric values.

FIG. 54 is a screenshot of a graphical user interface (GUI) program Rxscreen in accordance with one embodiment of the present specification.The “Program Rx” screen is accessed by pressing the Program Rx tab 5450.On this screen, in one embodiment, the user can program three distincttreatments schemes (denoted by buttons Save Rx1 5452, Save Rx2 5454, andSave Rx3 5456) with varying Flow 5453, On-Time 5455, Off-Time 5457 andnumbers of these Cycles 5459. To program a treatment, a user inputs thedesired parameters 5453, 5455, 5457, 5459 and presses the correspondingSave Rx button 5452, 5454, 5456. When the Save Rx buttons 5452, 5454,5456 are pressed, the GUI writes the selected parameter values to adedicated file on the disk. Therefore, the programmed data isnon-volatile and will be available at any time in the future until it isoverwritten.

FIG. 55 is a screenshot of a graphical user interface (GUI) deliver Rxscreen in accordance with one embodiment of the present specification.The “Deliver Rx” screen is accessed by pressing the Deliver Rx tab 5550and is used to launch the programmatic delivery of steam for ablation.In one embodiment, the indicators of Flow 5553, On-Time 5555, Off-Time5557 and Cycles 5559 are all set to zero by default to preventaccidental launching of a previously run program. To load a program thatwas previously programmed in the Program Rx screen, the user selects atreatment and presses the corresponding button 5552, 5554, 5556. In oneembodiment, once pressed, the button latches and changes color to greenwhile the parameter indicators populate with the values of the program.To start the treatment, the user presses the Deliver Rx button 5558 onthe GUI or, in one embodiment, presses the optional foot switch (footswitch 4022 in FIG. 40A). Once treatment has started, the Deliver Rxbutton 5558 latches and changes color to green. The light labeled “RxOn” 5509 in the System Alarm section 5508 illuminates and steamgeneration commences. The Enable Pump button 5504 will beprogrammatically turned on and off according to the program. When theprogram has finished, the Deliver Rx button 5558 will unlatch and changecolor to gray. The light labeled “Rx On” 5509 will turn off and steamgeneration will stop. The light labeled “Rx On” 5509 is included so thatthe user may press other tabs to switch to other screens and still beable to confirm that the treatment program is running or has finished.

The above examples are merely illustrative of the many applications ofthe system of the present invention. Although only a few embodiments ofthe present invention have been described herein, it should beunderstood that the present invention might be embodied in many otherspecific forms without departing from the spirit or scope of theinvention. Therefore, the present examples and embodiments are to beconsidered as illustrative and not restrictive, and the invention may bemodified within the scope of the appended claims.

We claim:
 1. An induction-based heating system comprising: a heatingchamber comprising a ferromagnetic core housed within anon-ferromagnetic housing; a resonant circuit comprising a capacitor andan induction coil positioned around said non-ferromagnetic housing; arectifier adapted to receive alternating current line voltage andprovide direct current power; a phase control circuit configured toplace said alternating current line voltage in electrical communicationwith said rectifier at each half wave of the alternating current linevoltage; and an H bridge inverter circuit configured to apply rectifiedline voltage across said resonant circuit, wherein said H bridgeinverter is adapted to apply rectified line voltage to said resonantcircuit and adapted to switch off when a magnetic field generated by theinduction coil is fully saturated.
 2. The induction-based heating systemof claim 1 wherein said heating chamber comprises a layer ofnon-thermoplastic insulation concentrically positioned around theferromagnetic core and separated from the ferromagnetic core by a space.3. The induction-based heating system of claim 2 wherein saidnon-ferromagnetic housing comprises a thermoplastic material and whereinsaid non-ferromagnetic housing is concentrically positioned around thelayer of non-thermoplastic insulation.
 4. The induction-based heatingsystem of claim 3 further comprising a second layer of non-thermoplasticinsulation concentrically positioned around the non-ferromagnetichousing and between said non-ferromagnetic housing and the inductioncoil.
 5. The induction-based heating system of claim 4 wherein at leastone of said layer of non-thermoplastic insulation and said second layerof non-thermoplastic insulation comprises mica.
 6. The induction-basedheating system of claim 3 wherein said thermoplastic material comprisesat least one of ABS, acetal, polyamide, PEEK, and polyvinylidenedifluoride (PVDF).
 7. The induction-based heating system of claim 1wherein said ferromagnetic core is a unitary member comprising aplurality of grooves encircling an outer periphery of the unitarymember.
 8. The induction-based heating system of claim 7 wherein saidferromagnetic core is a cylindrical unitary member having a first facetransverse to a length of the cylindrical unitary member and a secondface opposing the first face and transverse to the length of thecylindrical unitary member, wherein at least one of the first face andsecond face comprises a groove adapted to direct a fluid from a surfaceof the first face to said plurality of grooves or from said plurality ofgrooves to a surface of the second face.
 9. The induction-based heatingsystem of claim 1 further comprising an induction coil supportstructure, wherein said induction coil support structure is configuredto support the induction coil and slidably receive said heating chamber.10. The induction-based heating system of claim 9 wherein said inductioncoil has a total length and wherein said heating chamber is adapted tomove within the induction coil support structure such that saidferromagnetic core is configured to move relative to the induction coilby at least five percent of the total length of the induction coil. 11.The induction-based heating system of claim 9 further comprising ahandle attached to said heating chamber, wherein said handle has a totallength and wherein said heating chamber is adapted to move within theinduction coil support structure such that said ferromagnetic core isconfigured to move relative to the induction coil support structure byat least five percent of the total length of the handle.
 12. Theinduction-based heating system of claim 9 further comprising a handleand a catheter, wherein said heating chamber is attached to the catheterand said handle, wherein said handle, heating chamber, and catheter areconfigured such that moving said handle causes said heating chamber tomove relative to the induction coil and causes said catheter to move.13. The induction-based heating system of claim 12 wherein saidinduction coil has a total length and wherein said heating chamber isadapted to move within the induction coil support structure such thatsaid ferromagnetic core is configured to move relative to the inductioncoil by at least five percent of the total length of the induction coil.14. The induction-based heating system of claim 1 wherein the H bridgeinverter circuit is configured to switch on and off at a frequencybetween 10 kHz and 100 kHz.
 15. The induction-based heating system ofclaim 1 wherein a conversion of energy in said magnetic field to energyin said heat has an efficiency of 60% or greater.
 16. Theinduction-based heating system of claim 1 wherein the magnetic field hasa vibration of 15 to 25 kHz.
 17. The induction-based heating system ofclaim 1 further comprising control circuitry, wherein the controlcircuitry is configured to turn off a transmission of electrical energyto the H bridge inverter circuit once the magnetic field is fullysaturated.
 18. The induction-based heating system of claim 1 wherein,when the H bridge inverter is turned off and the magnetic fieldcollapses, a kickback pulse is generated and wherein at least onecapacitor is configured to absorb energy from said kickback pulse. 19.The induction-based heating system of claim 18 wherein said at least onecapacitor is configured to discharge electrical energy into saidinduction coil.
 20. The induction-based heating system of claim 1wherein said phase control circuit is configured to turn on the linevoltage to the rectifier and H bridge inverter circuit when saidcapacitor has discharged at least 90% of said electrical energy intosaid induction coil.
 21. The induction-based heating system of claim 1wherein said phase control circuit comprises a triac phase controlcircuit.
 22. The induction-based heating system of claim 1 wherein saidphase control circuit is configured to turn off at zero-point crossingsof said line voltage.
 23. The induction-based heating system of claim 21further comprising a drive circuit, wherein said drive circuit isconfigured to trigger the phase control circuit.
 24. The induction-basedheating system of claim 1 wherein said H-bridge inverter comprises fourswitches and wherein every 10 μsec to 50 μsec two of said four switchesare switched closed and two of said four switches are switched open. 25.The induction-based heating system of claim 24 wherein every 10 μsec to50 μsec the magnetic field is driven to zero and a polarity of themagnetic field is reversed.
 26. The induction-based heating system ofclaim 1 wherein, at each half-wave of the line voltage, the H bridgeinverter circuit actively drives up the resonant circuit to replenishlost energy.
 27. The induction-based heating system of claim 1 whereinthe non-ferromagnetic housing has a length ranging from 2.75 inches to3.75 inches, an inner diameter ranging from 7/32 inches to 11/32 inches,and an outer diameter ranging from ⅜ inches to 0.5 inches.
 28. Theinduction-based heating system of claim 27 wherein the ferromagneticcore has a length ranging from 1.5 inches to 2.5 inches and a diameterranging from 3/16 inches to 5/16 inches.
 29. The induction-based heatingsystem of claim 1 wherein the ferromagnetic core has a surface area tovolume ratio that is equal to, or greater than, 2(D₁+L)/D₂×L, where D₁is a shortest cross-sectional dimension of the ferromagnetic core, D₂ isa longest cross-sectional dimension of the ferromagnetic core, and L isa length of the ferromagnetic core.
 30. A method of performinginduction-based heating comprising: providing a closed loop fluidchannel, wherein the closed loop fluid channel comprises a heatingchamber having a non-ferromagnetic housing with an input port on a firstend and an output port on a second end and a ferromagnetic core housedwithin the non-ferromagnetic housing, a catheter attached to the outputport, a handle attached to the input port, a fluid channel positionedwithin said handle, a fluid source in fluid communication with the fluidchannel, and an induction coil support structure, wherein the inductioncoil support structure is configured to attach to an endoscope, whereinthe induction coil support structure supports an induction coil, andwherein the heating chamber is slidably positioned within the inductioncoil support structure, thereby positioning said induction coil aroundthe non-ferromagnetic housing; inserting the catheter into a channel ofan endoscope; repeatedly electrically driving a circuit in electricalcommunication with the induction coil to generate a magnetic field inthe induction coil and cause heat to be generated in said ferromagneticcore; physically moving the handle to cause said catheter to move withinsaid channel of the endoscope, wherein moving said handle causes theheating chamber to move relative to the induction coil; and initiating aflow of fluid through said closed loop fluid channel, wherein said flowof fluid passes through said ferromagnetic core and absorbs a portion ofsaid heat generated in said ferromagnetic core.
 31. The method ofperforming induction-based heating of claim 30 wherein the fluid iswater and wherein said water is transformed into steam as it passesthrough the heating chamber and into said catheter.
 32. The method ofperforming induction-based heating of claim 31 wherein said steam has awater content in a range of 1% to 95% when it exits from said catheter.33. The method of performing induction-based heating of claim 31 whereinsaid steam has a temperature in a range of 99° C. to 101° C.
 34. Themethod of performing induction-based heating of claim 30 wherein saidhandle has a total length and wherein said heating chamber is adapted tomove within the induction coil support structure such that saidferromagnetic core is configured to move relative to the induction coilsupport structure by at least five percent of the total length of thehandle.
 35. The method of performing induction-based heating of claim 30wherein said induction coil has a total length and wherein said heatingchamber is adapted to move within the induction coil support structuresuch that said ferromagnetic core is configured to move relative to theinduction coil by at least five percent of the total length of theinduction coil.
 36. The method of performing induction-based heating ofclaim 30 wherein said heating chamber comprises a layer ofnon-thermoplastic insulation concentrically positioned around theferromagnetic core and separated from the ferromagnetic core by a space.37. The method of performing induction-based heating of claim 36 whereinsaid non-ferromagnetic housing comprises a thermoplastic material andwherein said non-ferromagnetic housing is concentrically positionedaround the layer of non-thermoplastic insulation.
 38. The method ofperforming induction-based heating of claim 37 further comprising asecond layer of non-thermoplastic insulation concentrically positionedaround the non-ferromagnetic housing and between said non-ferromagnetichousing and the induction coil.
 39. The method of performinginduction-based heating of claim 38 wherein at least one of said layerof non-thermoplastic insulation and said second layer ofnon-thermoplastic insulation comprises mica.
 40. The method ofperforming induction-based heating of claim 37 wherein saidthermoplastic material comprises at least one of ABS, acetal, polyamide,PEEK, and PVDF.